diff --git a/CHANGELOG.md b/CHANGELOG.md
index e8b478193..092c81a69 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,20 @@ and Yorkie adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html)
 
 ## [Unreleased]
 
+## [0.4.21] - 2024-06-03
+
+### Added
+
+- Handle concurrent Tree.RemoveStyle by @hackerwins in https://github.com/yorkie-team/yorkie/pull/883
+
+### Changed
+
+- Return ErrClientNotActivated for deactivated clients on WatchDocument by @hackerwins in https://github.com/yorkie-team/yorkie/pull/877
+
+### Fixed
+
+- Fix incorrect tree snapshot encoding/decoding by @raararaara in https://github.com/yorkie-team/yorkie/pull/881
+
 ## [0.4.20] - 2024-05-24
 
 ### Added
diff --git a/Makefile b/Makefile
index 0a76e31ab..3c8f36544 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-YORKIE_VERSION := 0.4.20
+YORKIE_VERSION := 0.4.21
 
 GO_PROJECT = github.com/yorkie-team/yorkie
 
diff --git a/api/docs/yorkie.base.yaml b/api/docs/yorkie.base.yaml
index 4bb63e775..d2d343527 100644
--- a/api/docs/yorkie.base.yaml
+++ b/api/docs/yorkie.base.yaml
@@ -2,7 +2,7 @@ openapi: 3.1.0
 info:
   title: Yorkie
   description: "Yorkie is an open source document store for building collaborative editing applications."
-  version: v0.4.20
+  version: v0.4.21
 servers:
   - url: https://api.yorkie.dev
     description: Production server
diff --git a/api/docs/yorkie/v1/admin.openapi.yaml b/api/docs/yorkie/v1/admin.openapi.yaml
index 187557dd6..de0402612 100644
--- a/api/docs/yorkie/v1/admin.openapi.yaml
+++ b/api/docs/yorkie/v1/admin.openapi.yaml
@@ -4,7 +4,7 @@ info:
     Yorkie is an open source document store for building collaborative
     editing applications.
   title: Yorkie
-  version: v0.4.20
+  version: v0.4.21
 servers:
   - description: Production server
     url: https://api.yorkie.dev
diff --git a/api/docs/yorkie/v1/resources.openapi.yaml b/api/docs/yorkie/v1/resources.openapi.yaml
index 54a2f1d44..84a1f79ab 100644
--- a/api/docs/yorkie/v1/resources.openapi.yaml
+++ b/api/docs/yorkie/v1/resources.openapi.yaml
@@ -4,7 +4,7 @@ info:
     Yorkie is an open source document store for building collaborative
     editing applications.
   title: Yorkie
-  version: v0.4.20
+  version: v0.4.21
 servers:
   - description: Production server
     url: https://api.yorkie.dev
diff --git a/api/docs/yorkie/v1/yorkie.openapi.yaml b/api/docs/yorkie/v1/yorkie.openapi.yaml
index 888433ccb..0b555178c 100644
--- a/api/docs/yorkie/v1/yorkie.openapi.yaml
+++ b/api/docs/yorkie/v1/yorkie.openapi.yaml
@@ -4,7 +4,7 @@ info:
     Yorkie is an open source document store for building collaborative
     editing applications.
   title: Yorkie
-  version: v0.4.20
+  version: v0.4.21
 servers:
   - description: Production server
     url: https://api.yorkie.dev
diff --git a/build/charts/yorkie-cluster/Chart.yaml b/build/charts/yorkie-cluster/Chart.yaml
index 73b2f2b28..35454eebd 100644
--- a/build/charts/yorkie-cluster/Chart.yaml
+++ b/build/charts/yorkie-cluster/Chart.yaml
@@ -11,8 +11,8 @@ maintainers:
 
 sources:
   - https://github.com/yorkie-team/yorkie
-version: 0.4.20
-appVersion: "0.4.20"
+version: 0.4.21
+appVersion: "0.4.21"
 kubeVersion: ">=1.23.0-0"
 
 keywords: