diff --git a/CHANGELOG.md b/CHANGELOG.md
index ed21872..7051ec6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 ## master
 
 ### Added
+- Add check for duplicate keys in Spreadsheet ([#38](https://github.com/AckeeCZ/ACKLocalization/pull/38), kudos to @AGr-AlexandrGrigoryev)
 - Replaces custom solution for getting auth credentials with [google auth library](https://github.com/googleapis/google-auth-library-swift) ([#36](https://github.com/AckeeCZ/ACKLocalization/pull/36), kudos to @babacros)
 
 ## 1.5.0
diff --git a/Sources/ACKLocalizationCore/ACKLocalization.swift b/Sources/ACKLocalizationCore/ACKLocalization.swift
index 95d3048..45df297 100644
--- a/Sources/ACKLocalizationCore/ACKLocalization.swift
+++ b/Sources/ACKLocalizationCore/ACKLocalization.swift
@@ -412,12 +412,26 @@ public final class ACKLocalization {
     /// Actually writes given `rows` to given `file`
     private func writeRows(_ rows: [LocRow], to file: String) throws {
         guard rows.count > 0 else { return }
-        
+
+        try checkDuplicateKeys(form: rows)
+
         try rows.map { $0.localizableRow }
             .joined(separator: "\n")
             .write(toFile: file, atomically: true, encoding: .utf8)
     }
-    
+
+    /// Check if given `rows` have a duplicated keys
+    public func checkDuplicateKeys(form rows: [LocRow]) throws {
+        let keys = rows.map { $0.key }
+        let uniqueKeys = Set(keys)
+
+        if keys.count != uniqueKeys.count {
+            let duplicates = Dictionary(grouping: rows, by: \.key)
+                .filter { $1.count > 1 }.keys
+            throw LocalizationError(message: "❌ Check your Google Spreadsheet, you have a duplicated keys: \(duplicates)")
+        }
+    }
+
     /// Displays error to stdout
     private func displayError(_ localizationError: LocalizationError) {
         let message = "❌ " + localizationError.message
diff --git a/Tests/ACKLocalizationCoreTests/ACKLocalizationTests.swift b/Tests/ACKLocalizationCoreTests/ACKLocalizationTests.swift
index 3764742..33bbe31 100644
--- a/Tests/ACKLocalizationCoreTests/ACKLocalizationTests.swift
+++ b/Tests/ACKLocalizationCoreTests/ACKLocalizationTests.swift
@@ -2,8 +2,9 @@ import ACKLocalizationCore
 import XCTest
 
 final class ACKLocalizationTests: XCTestCase {
+    let localization = ACKLocalization()
+
     func test_transform_emptyRow() throws {
-        let localization = ACKLocalization()
         let mappedValues = try localization.transformValues(
             .init(
                 values: [
@@ -21,4 +22,22 @@ final class ACKLocalizationTests: XCTestCase {
             [LocRow(key: "key", value: "")]
         )
     }
+
+    func testForDuplicateKeys() throws {
+        let locRow = [
+            LocRow(key: "key_1", value: "value1"),
+            LocRow(key: "key_1", value: "value2"),
+            LocRow(key: "key_2", value: "value3")
+        ]
+        XCTAssertThrowsError(try localization.checkDuplicateKeys(form: locRow))
+    }
+
+    func testForUniqueKeys() throws {
+        let locRow = [
+            LocRow(key: "key_1", value: "value1"),
+            LocRow(key: "key_2", value: "value2"),
+            LocRow(key: "key_3", value: "value3")
+        ]
+        XCTAssertNoThrow(try localization.checkDuplicateKeys(form: locRow))
+    }
 }