diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
index 04d972f4253..8d51ba18087 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
@@ -1326,6 +1326,27 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirJsErrors.JS_NAME_CLASH) { firDiagnostic ->
+        JsNameClashImpl(
+            firDiagnostic.a,
+            firDiagnostic.b.map { firBasedSymbol ->
+                firSymbolBuilder.buildSymbol(firBasedSymbol)
+            },
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
+    add(FirJsErrors.JS_FAKE_NAME_CLASH) { firDiagnostic ->
+        JsFakeNameClashImpl(
+            firDiagnostic.a,
+            firSymbolBuilder.buildSymbol(firDiagnostic.b),
+            firDiagnostic.c.map { firBasedSymbol ->
+                firSymbolBuilder.buildSymbol(firBasedSymbol)
+            },
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.OPT_IN_USAGE) { firDiagnostic ->
         OptInUsageImpl(
             firDiagnostic.a,
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
index a2aaa3c6477..ec4a905e8dc 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
@@ -956,6 +956,19 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = NameContainsIllegalChars::class
     }
 
+    interface JsNameClash : KtFirDiagnostic<KtElement> {
+        override val diagnosticClass get() = JsNameClash::class
+        val name: String
+        val existing: List<KtSymbol>
+    }
+
+    interface JsFakeNameClash : KtFirDiagnostic<KtElement> {
+        override val diagnosticClass get() = JsFakeNameClash::class
+        val name: String
+        val override: KtSymbol
+        val existing: List<KtSymbol>
+    }
+
     interface OptInUsage : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = OptInUsage::class
         val optInMarkerFqName: FqName
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
index 2a9e382cf80..70eea3d3c34 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
@@ -1148,6 +1148,21 @@ internal class NameContainsIllegalCharsImpl(
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<KtElement>(firDiagnostic, token), KtFirDiagnostic.NameContainsIllegalChars
 
+internal class JsNameClashImpl(
+    override val name: String,
+    override val existing: List<KtSymbol>,
+    firDiagnostic: KtPsiDiagnostic,
+    token: KtLifetimeToken,
+) : KtAbstractFirDiagnostic<KtElement>(firDiagnostic, token), KtFirDiagnostic.JsNameClash
+
+internal class JsFakeNameClashImpl(
+    override val name: String,
+    override val override: KtSymbol,
+    override val existing: List<KtSymbol>,
+    firDiagnostic: KtPsiDiagnostic,
+    token: KtLifetimeToken,
+) : KtAbstractFirDiagnostic<KtElement>(firDiagnostic, token), KtFirDiagnostic.JsFakeNameClash
+
 internal class OptInUsageImpl(
     override val optInMarkerFqName: FqName,
     override val message: String,
diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirJsDiagnosticsList.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirJsDiagnosticsList.kt
index 2c63c36582c..3124809348b 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirJsDiagnosticsList.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirJsDiagnosticsList.kt
@@ -58,6 +58,15 @@ object JS_DIAGNOSTICS_LIST : DiagnosticList("FirJsErrors") {
             parameter<String>("name")
         }
         val NAME_CONTAINS_ILLEGAL_CHARS by error<KtElement>(PositioningStrategy.DECLARATION_SIGNATURE_OR_DEFAULT)
+        val JS_NAME_CLASH by error<KtElement>(PositioningStrategy.DECLARATION_SIGNATURE_OR_DEFAULT) {
+            parameter<String>("name")
+            parameter<Collection<FirBasedSymbol<*>>>("existing")
+        }
+        val JS_FAKE_NAME_CLASH by error<KtElement>(PositioningStrategy.DECLARATION_SIGNATURE_OR_DEFAULT) {
+            parameter<String>("name")
+            parameter<FirBasedSymbol<*>>("override")
+            parameter<Collection<FirBasedSymbol<*>>>("existing")
+        }
     }
 
     val SUPERTYPES by object : DiagnosticGroup("Supertypes") {
diff --git a/compiler/fir/checkers/checkers.js/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrors.kt b/compiler/fir/checkers/checkers.js/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrors.kt
index 3b22f8831d1..96d32404a08 100644
--- a/compiler/fir/checkers/checkers.js/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrors.kt
+++ b/compiler/fir/checkers/checkers.js/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrors.kt
@@ -52,6 +52,8 @@ object FirJsErrors {
     val JS_NAME_PROHIBITED_FOR_EXTENSION_PROPERTY by error0<KtElement>()
     val JS_BUILTIN_NAME_CLASH by error1<KtElement, String>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
     val NAME_CONTAINS_ILLEGAL_CHARS by error0<KtElement>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
+    val JS_NAME_CLASH by error2<KtElement, String, Collection<FirBasedSymbol<*>>>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
+    val JS_FAKE_NAME_CLASH by error3<KtElement, String, FirBasedSymbol<*>, Collection<FirBasedSymbol<*>>>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
 
     // Supertypes
     val WRONG_MULTIPLE_INHERITANCE by error1<KtElement, FirCallableSymbol<*>>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
diff --git a/compiler/fir/checkers/checkers.js/src/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrorsDefaultMessages.kt b/compiler/fir/checkers/checkers.js/src/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrorsDefaultMessages.kt
index 7ff702ae436..4974a97ab8f 100644
--- a/compiler/fir/checkers/checkers.js/src/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrorsDefaultMessages.kt
+++ b/compiler/fir/checkers/checkers.js/src/org/jetbrains/kotlin/fir/analysis/diagnostics/js/FirJsErrorsDefaultMessages.kt
@@ -37,6 +37,8 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_EXTERNAL_
 import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_MODULE_PROHIBITED_ON_NON_NATIVE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_MODULE_PROHIBITED_ON_VAR
 import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.NESTED_JS_MODULE_PROHIBITED
+import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_FAKE_NAME_CLASH
+import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_NAME_CLASH
 import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_NAME_IS_NOT_ON_ALL_ACCESSORS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_NAME_ON_ACCESSOR_AND_PROPERTY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.js.FirJsErrors.JS_NAME_ON_PRIMARY_CONSTRUCTOR_PROHIBITED
@@ -201,6 +203,19 @@ object FirJsErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             CommonRenderers.STRING
         )
         map.put(NAME_CONTAINS_ILLEGAL_CHARS, "Name contains illegal chars that cannot appear in JavaScript identifier.")
+        map.put(
+            JS_NAME_CLASH,
+            "JavaScript name ({0}) generated for this declaration clashes with another declarations: {1}",
+            CommonRenderers.STRING,
+            FirDiagnosticRenderers.SYMBOLS
+        )
+        map.put(
+            JS_FAKE_NAME_CLASH,
+            "JavaScript name {0} is generated for different inherited members: {1} and {2}",
+            CommonRenderers.STRING,
+            FirDiagnosticRenderers.SYMBOL,
+            FirDiagnosticRenderers.SYMBOLS
+        )
 
         map.put(JS_NAME_IS_NOT_ON_ALL_ACCESSORS, "'@JsName' should be on all the property accessors.")
         map.put(JS_NAME_PROHIBITED_FOR_NAMED_NATIVE, "'@JsName' is prohibited for external declaration with explicit name.")
diff --git a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt
index 04a14dad1d7..1f75219f46b 100644
--- a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt
+++ b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt
@@ -179,6 +179,8 @@ val FIR_NON_SUPPRESSIBLE_ERROR_NAMES: Set<String> = setOf(
     "JS_NAME_PROHIBITED_FOR_EXTENSION_PROPERTY",
     "JS_BUILTIN_NAME_CLASH",
     "NAME_CONTAINS_ILLEGAL_CHARS",
+    "JS_NAME_CLASH",
+    "JS_FAKE_NAME_CLASH",
     "OPT_IN_USAGE_ERROR",
     "OPT_IN_OVERRIDE_ERROR",
     "OPT_IN_CAN_ONLY_BE_USED_AS_ANNOTATION",