diff --git a/.changeset/lucky-guests-suffer.md b/.changeset/lucky-guests-suffer.md
new file mode 100644
index 0000000000..3f6e50e218
--- /dev/null
+++ b/.changeset/lucky-guests-suffer.md
@@ -0,0 +1,6 @@
+---
+"effect": patch
+---
+
+- Make `MergeRight`, `MergeLeft` and `MergeRecord` in `Types` module homomorphic (preserve original `readonly` and optionality modifiers)
+- `MergeRecord` now is alias for `MergeLeft`
diff --git a/packages/effect/dtslint/Types.ts b/packages/effect/dtslint/Types.ts
index d90aa81376..ef5b568ddd 100644
--- a/packages/effect/dtslint/Types.ts
+++ b/packages/effect/dtslint/Types.ts
@@ -63,6 +63,9 @@ hole<Types.Equals<{ a: number }, { b: number }>>()
 // $ExpectType { a: number; b: number; }
 hole<Types.MergeLeft<{ a: number; b: number }, { a: string }>>()
 
+// $ExpectType { readonly a?: number; b: number; readonly c?: string; }
+hole<Types.MergeLeft<{ readonly a?: number; b: number }, { readonly c?: string }>>()
+
 // -------------------------------------------------------------------------------------
 // MergeRight
 // -------------------------------------------------------------------------------------
@@ -70,6 +73,9 @@ hole<Types.MergeLeft<{ a: number; b: number }, { a: string }>>()
 // $ExpectType { a: string; b: number; }
 hole<Types.MergeRight<{ a: number; b: number }, { a: string }>>()
 
+// $ExpectType { readonly a?: string; b: number; }
+hole<Types.MergeRight<{ a: number; b: number }, { readonly a?: string }>>()
+
 // -------------------------------------------------------------------------------------
 // Mutable
 // -------------------------------------------------------------------------------------
diff --git a/packages/effect/src/Types.ts b/packages/effect/src/Types.ts
index 423c8ce414..2785fade80 100644
--- a/packages/effect/src/Types.ts
+++ b/packages/effect/src/Types.ts
@@ -156,11 +156,7 @@ export type Has<A, Key extends string> = (Key extends infer K ? K extends keyof
  * @since 2.0.0
  * @category models
  */
-export type MergeLeft<K, H> = Simplify<
-  {
-    [k in keyof K | keyof H]: k extends keyof K ? K[k] : k extends keyof H ? H[k] : never
-  }
->
+export type MergeLeft<Source, Target> = MergeRight<Target, Source>
 
 /**
  * Merges two object where the keys of the right object take precedence in the case of a conflict.
@@ -172,9 +168,10 @@ export type MergeLeft<K, H> = Simplify<
  * @since 2.0.0
  * @category models
  */
-export type MergeRight<K, H> = Simplify<
-  {
-    [k in keyof K | keyof H]: k extends keyof H ? H[k] : k extends keyof K ? K[k] : never
+export type MergeRight<Target, Source> = Simplify<
+  & Source
+  & {
+    [Key in keyof Target as Key extends keyof Source ? never : Key]: Target[Key]
   }
 >
 
@@ -182,12 +179,7 @@ export type MergeRight<K, H> = Simplify<
  * @since 2.0.0
  * @category models
  */
-export type MergeRecord<K, H> = {
-  [k in keyof K | keyof H]: k extends keyof K ? K[k]
-    : k extends keyof H ? H[k]
-    : never
-} extends infer X ? X
-  : never
+export type MergeRecord<Source, Target> = MergeLeft<Source, Target>
 
 /**
  * Describes the concurrency to use when executing multiple Effect's.