diff --git a/eng/testing/linker/SupportFiles/Directory.Build.targets b/eng/testing/linker/SupportFiles/Directory.Build.targets
index 90ce573551e90d..f1603cde43ad9d 100644
--- a/eng/testing/linker/SupportFiles/Directory.Build.targets
+++ b/eng/testing/linker/SupportFiles/Directory.Build.targets
@@ -19,6 +19,17 @@
     </ItemGroup>
   </Target>
 
+  <!-- This will need to change to AfterTargets=PrepareForILLink when we get a new SDK -->
+  <Target Name="EnsureAllAssembliesAreLinked"
+          AfterTargets="_SetILLinkDefaults"> 
+    <ItemGroup>
+      <!-- This will need to change to ManagedAssemblyToLink and TrimMode=link when we get a new SDK -->
+      <_ManagedAssembliesToLink>
+        <action>link</action>
+      </_ManagedAssembliesToLink>
+    </ItemGroup>
+  </Target>
+
   <Target Name="PublishTrimmed" DependsOnTargets="RestoreProject;UpdateRuntimePack;Publish" />
 
-</Project>
\ No newline at end of file
+</Project>
diff --git a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/DebuggerTypeProxyAttribute.cs b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/DebuggerTypeProxyAttribute.cs
index 500a946951bcff..1f99516869be62 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/DebuggerTypeProxyAttribute.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/DebuggerTypeProxyAttribute.cs
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace System.Diagnostics
 {
     [AttributeUsage(AttributeTargets.Struct | AttributeTargets.Class | AttributeTargets.Assembly, AllowMultiple = true)]
@@ -8,7 +10,8 @@ public sealed class DebuggerTypeProxyAttribute : Attribute
     {
         private Type? _target;
 
-        public DebuggerTypeProxyAttribute(Type type)
+        public DebuggerTypeProxyAttribute(
+            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] Type type)
         {
             if (type == null)
             {
@@ -18,11 +21,15 @@ public DebuggerTypeProxyAttribute(Type type)
             ProxyTypeName = type.AssemblyQualifiedName!;
         }
 
-        public DebuggerTypeProxyAttribute(string typeName)
+        public DebuggerTypeProxyAttribute(
+            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] string typeName)
         {
             ProxyTypeName = typeName;
         }
 
+        // The Proxy is only invoked by the debugger, so it needs to have its
+        // members preserved
+        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
         public string ProxyTypeName { get; }
 
         public Type? Target
diff --git a/src/libraries/System.Runtime/ref/System.Runtime.cs b/src/libraries/System.Runtime/ref/System.Runtime.cs
index ee91e1dd2f824e..548f48bede5543 100644
--- a/src/libraries/System.Runtime/ref/System.Runtime.cs
+++ b/src/libraries/System.Runtime/ref/System.Runtime.cs
@@ -5715,8 +5715,9 @@ public DebuggerStepThroughAttribute() { }
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Struct, AllowMultiple=true)]
     public sealed partial class DebuggerTypeProxyAttribute : System.Attribute
     {
-        public DebuggerTypeProxyAttribute(string typeName) { }
-        public DebuggerTypeProxyAttribute(System.Type type) { }
+        public DebuggerTypeProxyAttribute([System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.All)] string typeName) { }
+        public DebuggerTypeProxyAttribute([System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.All)] System.Type type) { }
+        [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.All)]
         public string ProxyTypeName { get { throw null; } }
         public System.Type? Target { get { throw null; } set { } }
         public string? TargetTypeName { get { throw null; } set { } }
diff --git a/src/libraries/System.Runtime/tests/TrimmingTests/DebuggerTypeProxyAttributeTests.cs b/src/libraries/System.Runtime/tests/TrimmingTests/DebuggerTypeProxyAttributeTests.cs
new file mode 100644
index 00000000000000..b80f4a1d61b00b
--- /dev/null
+++ b/src/libraries/System.Runtime/tests/TrimmingTests/DebuggerTypeProxyAttributeTests.cs
@@ -0,0 +1,73 @@
+using System;
+using System.Diagnostics;
+
+/// <summary>
+/// Tests that types used by DebuggerTypeProxyAttribute are not trimmed out
+/// when Debugger.IsSupported is true (the default).
+/// </summary>
+class Program
+{
+    static int Main(string[] args)
+    {
+        MyClass myClass = new MyClass() { Name = "trimmed" };
+        MyClassWithProxyString myClassWithString = new MyClassWithProxyString() { Name = "trimmed" };
+
+        Type[] allTypes = typeof(MyClass).Assembly.GetTypes();
+        bool foundDebuggerProxy = false;
+        bool foundStringDebuggerProxy = false;
+        for (int i = 0; i < allTypes.Length; i++)
+        {
+            Type currentType = allTypes[i];
+            if (currentType.FullName == "Program+MyClass+DebuggerProxy" &&
+                currentType.GetProperties().Length == 1 &&
+                currentType.GetConstructors().Length == 1)
+            {
+                foundDebuggerProxy = true;
+            }
+            else if (currentType.FullName == "Program+MyClassWithProxyStringProxy" &&
+                currentType.GetProperties().Length == 1 &&
+                currentType.GetConstructors().Length == 1)
+            {
+                foundStringDebuggerProxy = true;
+            }
+        }
+
+        return foundDebuggerProxy && foundStringDebuggerProxy ? 100 : -1;
+    }
+
+    [DebuggerTypeProxy(typeof(DebuggerProxy))]
+    public class MyClass
+    {
+        public string Name { get; set; }
+
+        private class DebuggerProxy
+        {
+            private MyClass _instance;
+
+            public DebuggerProxy(MyClass instance)
+            {
+                _instance = instance;
+            }
+
+            public string DebuggerName => _instance.Name + " Proxy";
+        }
+    }
+
+    [DebuggerTypeProxy("Program+MyClassWithProxyStringProxy")]
+    public class MyClassWithProxyString
+    {
+        public string Name { get; set; }
+    }
+
+    internal class MyClassWithProxyStringProxy
+    {
+        private MyClassWithProxyString _instance;
+
+        public MyClassWithProxyStringProxy(MyClassWithProxyString instance)
+        {
+            _instance = instance;
+        }
+
+        public string DebuggerName => _instance.Name + " StringProxy";
+    }
+}
diff --git a/src/libraries/System.Runtime/tests/TrimmingTests/DefaultValueAttributeCtorTest.cs b/src/libraries/System.Runtime/tests/TrimmingTests/DefaultValueAttributeCtorTest.cs
index c30fb88e0b836b..aaf82add5a0519 100644
--- a/src/libraries/System.Runtime/tests/TrimmingTests/DefaultValueAttributeCtorTest.cs
+++ b/src/libraries/System.Runtime/tests/TrimmingTests/DefaultValueAttributeCtorTest.cs
@@ -10,6 +10,10 @@ class Program
 {
     static int Main(string[] args)
     {
+        // workaround TypeConverterAttribute not being annotated correctly
+        // https://github.com/dotnet/runtime/issues/39125
+        var _ = new MyStringConverter();
+
         TypeDescriptor.AddAttributes(typeof(string), new TypeConverterAttribute(typeof(MyStringConverter)));
 
         var attribute = new DefaultValueAttribute(typeof(string), "Hello, world!");
diff --git a/src/libraries/System.Runtime/tests/TrimmingTests/System.Runtime.TrimmingTests.proj b/src/libraries/System.Runtime/tests/TrimmingTests/System.Runtime.TrimmingTests.proj
index cfd1a4d2a7b81b..ce96e07448a3cc 100644
--- a/src/libraries/System.Runtime/tests/TrimmingTests/System.Runtime.TrimmingTests.proj
+++ b/src/libraries/System.Runtime/tests/TrimmingTests/System.Runtime.TrimmingTests.proj
@@ -6,6 +6,8 @@
     <TestConsoleAppSourceFiles Include="AppDomainGetThreadWindowsPrincipalTest.cs">
       <SkipOnTestRuntimes>osx-x64;linux-x64</SkipOnTestRuntimes>
     </TestConsoleAppSourceFiles>
+    <TestConsoleAppSourceFiles Include="DebuggerTypeProxyAttributeTests.cs" />
+    <TestConsoleAppSourceFiles Include="DefaultValueAttributeCtorTest.cs" />
     <TestConsoleAppSourceFiles Include="GenericArraySortHelperTest.cs" />
     <TestConsoleAppSourceFiles Include="StackFrameHelperTest.cs">
       <!-- There is a bug with the linker where it is corrupting the pdbs while trimming