diff --git a/features/apply_with_dependent_stacks.feature b/features/apply_with_dependent_stacks.feature
new file mode 100644
index 00000000..1affaf92
--- /dev/null
+++ b/features/apply_with_dependent_stacks.feature
@@ -0,0 +1,169 @@
+Feature: Apply command
+
+  Background:
+    Given a file named "stack_master.yml" with:
+      """
+      stacks:
+        us_east_1:
+          myapp_vpc:
+            template: myapp_vpc.rb
+          myapp_web:
+            template: myapp_web.rb
+      """
+    And a directory named "parameters"
+    And a file named "parameters/myapp_vpc.yml" with:
+      """
+      ip_range: 10.160.0.0/16
+      """
+    And a file named "parameters/myapp_web.yml" with:
+      """
+      VpcId:
+        stack_output: myapp_vpc/vpc_id
+      """
+    And a directory named "templates"
+    And a file named "templates/myapp_vpc.rb" with:
+      """
+      SparkleFormation.new(:myapp_vpc) do
+        description "Test template"
+        set!('AWSTemplateFormatVersion', '2010-09-09')
+
+        parameters.ip_range do
+          description 'IP CIDR'
+          type 'String'
+        end
+
+        resources.vpc do
+          type 'AWS::EC2::VPC'
+          properties do
+            cidr_block ref!(:ip_range)
+          end
+        end
+
+        outputs do
+          vpc_id do
+            description 'A VPC ID'
+            value ref!(:vpc)
+          end
+        end
+      end
+      """
+    And a file named "templates/myapp_web.rb" with:
+      """
+      SparkleFormation.new(:myapp_web) do
+        description "Test template"
+        set!('AWSTemplateFormatVersion', '2010-09-09')
+
+        parameters.vpc_id do
+          description 'VPC ID'
+          type 'AWS::EC2::VPC::Id'
+        end
+
+        resources.test_sg do
+          type 'AWS::EC2::SecurityGroup'
+          properties do
+            group_description 'Test SG'
+            vpc_id ref!(:vpc_id)
+          end
+        end
+      end
+      """
+
+   Scenario: Update a stack that does not cause a replacement
+    Given I stub the following stack events:
+      | stack_id | event_id | stack_name | logical_resource_id | resource_status | resource_type              | timestamp           |
+      | 1        | 1        | myapp-vpc  | Vpc                 | UPDATE_COMPLETE | AWS::EC2::VPC    | 2020-10-29 00:00:00 |
+      | 1        | 1        | myapp-vpc  | myapp-vpc           | UPDATE_COMPLETE | AWS::CloudFormation::Stack | 2020-10-29 00:00:00 |
+    And I stub the following stacks:
+      | stack_id | stack_name | parameters       | region    | outputs        |
+      | 1        | myapp-vpc  | KeyName=my-key   | us-east-1 | VpcId=vpc-1111 |
+    And I stub the following stacks:
+      | stack_id | stack_name | parameters       | region    |
+      | 2        | myapp-web  | VpcId=vpc-1111   | us-east-1 |
+    And I stub a template for the stack "myapp-vpc":
+      """
+      {
+        "Description": "Test template",
+        "AWSTemplateFormatVersion": "2010-09-09",
+        "Parameters": {
+          "IpRange": {
+            "Description": "Ip CIDR",
+            "Type": "String"
+          }
+        },
+        "Resources": {
+          "Vpc": {
+            "Type": "AWS::EC2::VPC",
+            "Properties": {
+              "CidrBlock": "10.161.0.0/16",
+              "EnableDnsSupport": "true"
+            }
+          }
+        },
+        "Outputs": {
+          "VpcId": {
+            "Value": { "Ref": "Vpc" }
+          }
+        }
+      }
+      """
+
+
+    When I run `stack_master apply us-east-1 myapp-vpc --trace`
+    And the output should contain all of these lines:
+      | Stack diff:                                                                  |
+      | -        "EnableDnsSupport": "true"                                          |
+      | Proposed change set:                                                         |
+      | Replace                                                                      |
+      | Apply change set (y/n)?                                                      |
+    And the output should not contain all of these lines:
+      | A dependent stack "myapp-web" is now out of date because of this change.     |
+      | Apply this stack now (y/n)?                                                  |
+    Then the exit status should be 0
+
+   Scenario: Update a stack that causes a replacement
+    Given I stub the following stack events:
+      | stack_id | event_id | stack_name | logical_resource_id | resource_status | resource_type              | timestamp           |
+      | 1        | 1        | myapp-vpc  | Vpc                 | CREATE_COMPLETE | AWS::EC2::VPC    | 2020-10-29 00:00:00 |
+      | 1        | 1        | myapp-vpc  | myapp-vpc           | CREATE_COMPLETE | AWS::CloudFormation::Stack | 2020-10-29 00:00:00 |
+    And I stub the following stacks:
+      | stack_id | stack_name | parameters       | region    | outputs        |
+      | 1        | myapp-vpc  | KeyName=my-key   | us-east-1 | VpcId=vpc-1111 |
+    And I stub the following stacks:
+      | stack_id | stack_name | parameters       | region    |
+      | 2        | myapp-web  | VpcId=vpc-9999   | us-east-1 |
+    And I stub a template for the stack "myapp-vpc":
+      """
+      {
+        "Description": "Test template",
+        "AWSTemplateFormatVersion": "2010-09-09",
+        "Parameters": {
+          "IpRange": {
+            "Description": "Ip CIDR",
+            "Type": "String"
+          }
+        },
+        "Resources": {
+          "Vpc": {
+            "Type": "AWS::EC2::VPC",
+            "Properties": {
+              "CidrBlock": "10.161.0.0/16"
+            }
+          }
+        },
+        "Outputs": {
+          "VpcId": {
+            "Value": { "Ref": "Vpc" }
+          }
+        }
+      }
+      """
+    When I run `stack_master apply us-east-1 myapp-vpc --trace`
+    And the output should contain all of these lines:
+      | Stack diff:                                                                  |
+      | -        "CidrBlock": "10.161.0.0/16"                                        |
+      | Proposed change set:                                                         |
+      | Replace                                                                      |
+      | Apply change set (y/n)?                                                      |
+      | A dependent stack "myapp-web" is now out of date because of this change.     |
+      | Apply this stack now (y/n)?                                                  |
+    Then the exit status should be 0
diff --git a/lib/stack_master.rb b/lib/stack_master.rb
index 0280d925..906a4a63 100644
--- a/lib/stack_master.rb
+++ b/lib/stack_master.rb
@@ -31,6 +31,7 @@ module StackMaster
 
   autoload :StackDiffer, 'stack_master/stack_differ'
   autoload :Validator, 'stack_master/validator'
+  autoload :StackDependency, 'stack_master/stack_dependency'
 
   require 'stack_master/template_compilers/sparkle_formation'
   require 'stack_master/template_compilers/json'
diff --git a/lib/stack_master/commands/apply.rb b/lib/stack_master/commands/apply.rb
index 7dded974..5b166f7d 100644
--- a/lib/stack_master/commands/apply.rb
+++ b/lib/stack_master/commands/apply.rb
@@ -51,12 +51,17 @@ def diff_stacks
         StackDiffer.new(proposed_stack, stack).output_diff
       end
 
+      def dependencies
+        @dependencies ||= StackDependency.new(@stack_definition, @config)
+      end
+
       def create_or_update_stack
         if stack_exists?
           update_stack
         else
           create_stack
         end
+        offer_to_run_dependent_stacks
       end
 
       def create_stack
@@ -162,6 +167,13 @@ def ensure_valid_template_body_size!
         end
       end
 
+      def offer_to_run_dependent_stacks
+        dependencies.outdated_stacks.each do |stack|
+          next unless ask?(%Q{A dependent stack "#{stack.stack_name}" is now out of date because of this change.\nApply this stack now (y/n)?})
+          self.class.new(@config, stack, @options)
+        end
+      end
+
       extend Forwardable
       def_delegators :@stack_definition, :stack_name, :region
     end
diff --git a/lib/stack_master/stack_dependency.rb b/lib/stack_master/stack_dependency.rb
new file mode 100644
index 00000000..8cb3cb77
--- /dev/null
+++ b/lib/stack_master/stack_dependency.rb
@@ -0,0 +1,71 @@
+module StackMaster
+  class StackDependency
+    StackOutputNotFound = Class.new(StandardError)
+
+    def initialize(stack_definition, config)
+      @stack_definition = stack_definition
+      @config = config
+    end
+
+    def outdated_stacks
+      @config.stacks.select do |stack|
+        dependent_stack = Stack.find(stack.region, stack.stack_name)
+        next unless dependent_stack
+        parameters = ParameterLoader.load(stack.parameter_files)
+        any_stack_output_outdated?(parameters, dependent_stack)
+      end
+    end
+
+    private
+
+    def any_stack_output_outdated?(params, stack)
+      params.any? do |key, value|
+        stack_output_outdated?(value['stack_output'], stack, @stack_definition.stack_name) ||
+          stack_outputs_outdated?(value['stack_outputs'], stack, @stack_definition.stack_name, key)
+      end
+    end
+
+    def stack_output_outdated?(stack_output, stack, stack_name)
+      stack_output &&
+        stack_output_is_our_stack?(stack_output, stack_name) &&
+        outdated?(stack, stack_output.split('/').last)
+    end
+
+    def stack_outputs_outdated?(stack_outputs, stack, stack_name, parameter_key)
+      dependent_parameter = stack_parameter(stack, parameter_key)
+      stack_outputs && stack_outputs.any? do |output|
+        index = stack_outputs.find_index(output)
+        this_output_value = dependent_parameter.split(',')[index]
+        stack_output_is_our_stack?(output, stack_name) &&
+          output_value(output.split('/').last.camelize) != this_output_value
+      end
+    end
+
+    def stack_output_is_our_stack?(stack_output, stack)
+      stack_output.gsub('_', '-') =~ %r(#{stack}/)
+    end
+
+    def outdated?(dependent_stack, output_key)
+      stack_output = output_value(output_key.camelize)
+      dependent_input = stack_parameter(dependent_stack, output_key)
+      dependent_input != stack_output
+    end
+
+    def stack_parameter(stack, key)
+      stack.parameters[key.camelize]
+    end
+
+    def output_value(key)
+      output_hash = updated_stack.outputs.select { |output_type| output_type[:output_key] == key }
+      if output_hash && ! output_hash.empty?
+        output_hash.first[:output_value]
+      else
+        raise StackOutputNotFound, "Stack exists (#{updated_stack.stack_name}), but output does not: #{key}"
+      end
+    end
+
+    def updated_stack
+      @stack ||= Stack.find(@stack_definition.region, @stack_definition.stack_name)
+    end
+  end
+end
diff --git a/spec/fixtures/parameters/myapp_web.yml b/spec/fixtures/parameters/myapp_web.yml
new file mode 100644
index 00000000..8db7cd76
--- /dev/null
+++ b/spec/fixtures/parameters/myapp_web.yml
@@ -0,0 +1,6 @@
+vpc_id:
+  stack_output: myapp_vpc/vpc_id
+subnet_ids:
+  stack_outputs:
+    - myapp_vpc/subnet_1
+    - myapp_vpc/subnet_2
diff --git a/spec/stack_master/commands/apply_spec.rb b/spec/stack_master/commands/apply_spec.rb
index ecd85c26..0a83b188 100644
--- a/spec/stack_master/commands/apply_spec.rb
+++ b/spec/stack_master/commands/apply_spec.rb
@@ -3,7 +3,7 @@
   let(:s3) { instance_double(Aws::S3::Client) }
   let(:region) { 'us-east-1' }
   let(:stack_name) { 'myapp-vpc' }
-  let(:config) { double(find_stack: stack_definition) }
+  let(:config) { double(find_stack: stack_definition, stacks: []) }
   let(:notification_arn) { 'test_arn' }
   let(:stack_definition) { StackMaster::StackDefinition.new(base_dir: '/base_dir', region: region, stack_name: stack_name) }
   let(:template_body) { '{}' }
diff --git a/spec/stack_master/stack_dependency_spec.rb b/spec/stack_master/stack_dependency_spec.rb
new file mode 100644
index 00000000..311efa78
--- /dev/null
+++ b/spec/stack_master/stack_dependency_spec.rb
@@ -0,0 +1,89 @@
+RSpec.describe StackMaster::StackDependency do
+  let(:region) { 'us-east-1' }
+  let(:vpc_stack_name) { 'myapp-vpc' }
+  let(:vpc_stack_definition) { StackMaster::StackDefinition.new(base_dir: '/base_dir', region: region, stack_name: vpc_stack_name) }
+  let(:vpc_stack) do
+    StackMaster::Stack.new(
+      stack_id: '1',
+      stack_name: vpc_stack_name,
+      outputs: [
+        {description: "", output_key: "VpcId", output_value: "vpc-123"},
+        {description: "", output_key: "Subnet1Id", output_value: "subnet-456"},
+        {description: "", output_key: "Subnet2Id", output_value: "subnet-789"},
+      ]
+    )
+  end
+  let(:web_stack_name) { 'myapp-web' }
+  let(:web_stack_definition) { StackMaster::StackDefinition.new(base_dir: '/base_dir', region: region, stack_name: web_stack_name) }
+  let(:web_stack) do
+    StackMaster::Stack.new(
+      stack_id: '2',
+      stack_name: web_stack_name,
+      parameters: {
+        "VpcId" => web_stack_vpc_id,
+        "SubnetIds" => web_stack_subnet_ids,
+      }
+    )
+  end
+  let(:web_param_file) {
+    <<-eos
+    vpc_id:
+      stack_output: myapp-vpc/vpc_id
+    subnet_ids:
+      stack_outputs:
+        - myapp-vpc/subnet_1_id
+        - myapp-vpc/subnet_2_id
+    eos
+  }
+  let(:config) { double(find: vpc_stack, stacks: [vpc_stack_definition, web_stack_definition]) }
+
+  subject { described_class.new(vpc_stack_definition, config) }
+
+  before do
+    allow(File).to receive(:exists?).and_call_original
+    allow(File).to receive(:read).with('/base_dir/parameters/myapp_web.yml').and_return(web_param_file)
+    allow(StackMaster::Stack).to receive(:find).with(region, web_stack_name).and_return(web_stack)
+    allow(StackMaster::Stack).to receive(:find).with(region, vpc_stack_name).and_return(vpc_stack)
+  end
+
+  context 'the stack exists' do
+    before do
+      expect(File).to receive(:exists?).with('/base_dir/parameters/myapp_web.yml').and_return(true)
+    end
+
+    context 'when the web stacks parameters are up to date' do
+      let(:web_stack_vpc_id) { "vpc-123" }
+      let(:web_stack_subnet_ids) { "subnet-456,subnet-789" }
+
+      it 'returns no outdated stacks' do
+        expect(subject.outdated_stacks).to eq []
+      end
+    end
+
+    context 'when the stack_output is out of date' do
+      let(:web_stack_vpc_id) { "vpc-321" }
+      let(:web_stack_subnet_ids) { "subnet-456,subnet-789" }
+
+      it 'returns one outdated stack' do
+        expect(subject.outdated_stacks).to eq [web_stack_definition]
+      end
+    end
+
+    context 'when one of the stack_outputs is out of date' do
+      let(:web_stack_vpc_id) { "vpc-123" }
+      let(:web_stack_subnet_ids) { "subnet-654,subnet-789" }
+
+      it 'returns one outdated stack' do
+        expect(subject.outdated_stacks).to eq [web_stack_definition]
+      end
+    end
+  end
+
+  context 'when no other stacks exist' do
+    let(:web_stack) { nil }
+
+    it 'returns no outdated stacks' do
+      expect(subject.outdated_stacks).to eq []
+    end
+  end
+end