diff --git a/README.md b/README.md
index 56f49d6..8b34cc4 100644
--- a/README.md
+++ b/README.md
@@ -93,30 +93,32 @@ When using with the Claude App, you need to set up your API key and URLs directl
 15. `mr_discussions` - List discussion items for a merge request
 16. `update_merge_request_note` - Modify an existing merge request thread note
 17. `create_merge_request_note` - Add a new note to an existing merge request thread
-18. `list_issues` - List issues in a GitLab project with filtering options
-19. `get_issue` - Get details of a specific issue in a GitLab project
-20. `update_issue` - Update an issue in a GitLab project
-21. `delete_issue` - Delete an issue from a GitLab project
-22. `list_issue_links` - List all issue links for a specific issue
-23. `list_issue_discussions` - List discussions for an issue in a GitLab project
-24. `get_issue_link` - Get a specific issue link
-25. `create_issue_link` - Create an issue link between two issues
-26. `delete_issue_link` - Delete an issue link
-27. `list_namespaces` - List all namespaces available to the current user
-28. `get_namespace` - Get details of a namespace by ID or path
-29. `verify_namespace` - Verify if a namespace path exists
-30. `get_project` - Get details of a specific project
-31. `list_projects` - List projects accessible by the current user
-32. `list_labels` - List labels for a project
-33. `get_label` - Get a single label from a project
-34. `create_label` - Create a new label in a project
-35. `update_label` - Update an existing label in a project
-36. `delete_label` - Delete a label from a project
-37. `list_group_projects` - List projects in a GitLab group with filtering options
-38. `list_wiki_pages` - List wiki pages in a GitLab project
-39. `get_wiki_page` - Get details of a specific wiki page
-40. `create_wiki_page` - Create a new wiki page in a GitLab project
-41. `update_wiki_page` - Update an existing wiki page in a GitLab project
-42. `delete_wiki_page` - Delete a wiki page from a GitLab project
-43. `get_repository_tree` - Get the repository tree for a GitLab project (list files and directories)
+18. `update_issue_note` - Update the content of an existing issue note
+19. `create_issue_note` - Add a new note to an existing issue thread
+20. `list_issues` - List issues in a GitLab project with filtering options
+21. `get_issue` - Get details of a specific issue in a GitLab project
+22. `update_issue` - Update an issue in a GitLab project
+23. `delete_issue` - Delete an issue from a GitLab project
+24. `list_issue_links` - List all issue links for a specific issue
+25. `list_issue_discussions` - List discussions for an issue in a GitLab project
+26. `get_issue_link` - Get a specific issue link
+27. `create_issue_link` - Create an issue link between two issues
+28. `delete_issue_link` - Delete an issue link
+29. `list_namespaces` - List all namespaces available to the current user
+30. `get_namespace` - Get details of a namespace by ID or path
+31. `verify_namespace` - Verify if a namespace path exists
+32. `get_project` - Get details of a specific project
+33. `list_projects` - List projects accessible by the current user
+34. `list_labels` - List labels for a project
+35. `get_label` - Get a single label from a project
+36. `create_label` - Create a new label in a project
+37. `update_label` - Update an existing label in a project
+38. `delete_label` - Delete a label from a project
+39. `list_group_projects` - List projects in a GitLab group with filtering options
+40. `list_wiki_pages` - List wiki pages in a GitLab project
+41. `get_wiki_page` - Get details of a specific wiki page
+42. `create_wiki_page` - Create a new wiki page in a GitLab project
+43. `update_wiki_page` - Update an existing wiki page in a GitLab project
+44. `delete_wiki_page` - Delete a wiki page from a GitLab project
+45. `get_repository_tree` - Get the repository tree for a GitLab project (list files and directories)
 <!-- TOOLS-END -->
diff --git a/index.ts b/index.ts
index 1aaebee..5a7a045 100644
--- a/index.ts
+++ b/index.ts
@@ -121,6 +121,8 @@ import {
   GetRepositoryTreeSchema,
   type GitLabTreeItem,
   type GetRepositoryTreeOptions,
+  UpdateIssueNoteSchema,
+  CreateIssueNoteSchema,
 } from "./schemas.js";
 
 /**
@@ -287,6 +289,16 @@ const allTools = [
     description: "Add a new note to an existing merge request thread",
     inputSchema: zodToJsonSchema(CreateMergeRequestNoteSchema),
   },
+  {
+    name: "update_issue_note",
+    description: "Modify an existing issue thread note",
+    inputSchema: zodToJsonSchema(UpdateIssueNoteSchema),
+  },
+  {
+    name: "create_issue_note",
+    description: "Add a new note to an existing issue thread",
+    inputSchema: zodToJsonSchema(CreateIssueNoteSchema),
+  },
   {
     name: "list_issues",
     description: "List issues in a GitLab project with filtering options",
@@ -1126,6 +1138,81 @@ async function updateMergeRequestNote(
   return GitLabDiscussionNoteSchema.parse(data);
 }
 
+/**
+ * Update an issue discussion note
+ * @param {string} projectId - The ID or URL-encoded path of the project
+ * @param {number} issueIid - The IID of an issue
+ * @param {string} discussionId - The ID of a thread
+ * @param {number} noteId - The ID of a thread note
+ * @param {string} body - The new content of the note
+ * @returns {Promise<GitLabDiscussionNote>} The updated note
+ */
+async function updateIssueNote(
+  projectId: string,
+  issueIid: number,
+  discussionId: string,
+  noteId: number,
+  body: string
+): Promise<GitLabDiscussionNote> {
+  projectId = decodeURIComponent(projectId); // Decode project ID
+  const url = new URL(
+    `${GITLAB_API_URL}/projects/${encodeURIComponent(
+      projectId
+    )}/issues/${issueIid}/discussions/${discussionId}/notes/${noteId}`
+  );
+
+  const payload = { body };
+
+  const response = await fetch(url.toString(), {
+    ...DEFAULT_FETCH_CONFIG,
+    method: "PUT",
+    body: JSON.stringify(payload),
+  });
+
+  await handleGitLabError(response);
+  const data = await response.json();
+  return GitLabDiscussionNoteSchema.parse(data);
+}
+
+/**
+ * Create a note in an issue discussion
+ * @param {string} projectId - The ID or URL-encoded path of the project
+ * @param {number} issueIid - The IID of an issue
+ * @param {string} discussionId - The ID of a thread
+ * @param {string} body - The content of the new note
+ * @param {string} [createdAt] - The creation date of the note (ISO 8601 format)
+ * @returns {Promise<GitLabDiscussionNote>} The created note
+ */
+async function createIssueNote(
+  projectId: string,
+  issueIid: number,
+  discussionId: string,
+  body: string,
+  createdAt?: string
+): Promise<GitLabDiscussionNote> {
+  projectId = decodeURIComponent(projectId); // Decode project ID
+  const url = new URL(
+    `${GITLAB_API_URL}/projects/${encodeURIComponent(
+      projectId
+    )}/issues/${issueIid}/discussions/${discussionId}/notes`
+  );
+
+  const payload: { body: string; created_at?: string } = { body };
+  if (createdAt) {
+    payload.created_at = createdAt;
+  }
+
+  const response = await fetch(url.toString(), {
+    ...DEFAULT_FETCH_CONFIG,
+    method: "POST",
+    body: JSON.stringify(payload),
+  });
+
+  await handleGitLabError(response);
+  const data = await response.json();
+  return GitLabDiscussionNoteSchema.parse(data);
+}
+
 /**
  * Add a new note to an existing merge request thread
  * 기존 병합 요청 스레드에 새 노트 추가
@@ -2461,6 +2548,38 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
         };
       }
 
+      case "update_issue_note": {
+        const args = UpdateIssueNoteSchema.parse(
+          request.params.arguments
+        );
+        const note = await updateIssueNote(
+          args.project_id,
+          args.issue_iid,
+          args.discussion_id,
+          args.note_id,
+          args.body
+        );
+        return {
+          content: [{ type: "text", text: JSON.stringify(note, null, 2) }],
+        };
+      }
+
+      case "create_issue_note": {
+        const args = CreateIssueNoteSchema.parse(
+          request.params.arguments
+        );
+        const note = await createIssueNote(
+          args.project_id,
+          args.issue_iid,
+          args.discussion_id,
+          args.body,
+          args.created_at
+        );
+        return {
+          content: [{ type: "text", text: JSON.stringify(note, null, 2) }],
+        };
+      }
+
       case "get_merge_request": {
         const args = GetMergeRequestSchema.parse(request.params.arguments);
         const mergeRequest = await getMergeRequest(
diff --git a/schemas.ts b/schemas.ts
index 071ee5f..6ae2fce 100644
--- a/schemas.ts
+++ b/schemas.ts
@@ -491,6 +491,22 @@ export const CreateMergeRequestNoteSchema = ProjectParamsSchema.extend({
   created_at: z.string().optional().describe("Date the note was created at (ISO 8601 format)"),
 });
 
+// Input schema for updating an issue discussion note
+export const UpdateIssueNoteSchema = ProjectParamsSchema.extend({
+  issue_iid: z.number().describe("The IID of an issue"),
+  discussion_id: z.string().describe("The ID of a thread"),
+  note_id: z.number().describe("The ID of a thread note"),
+  body: z.string().describe("The content of the note or reply"),
+});
+
+// Input schema for adding a note to an existing issue discussion
+export const CreateIssueNoteSchema = ProjectParamsSchema.extend({
+  issue_iid: z.number().describe("The IID of an issue"),
+  discussion_id: z.string().describe("The ID of a thread"),
+  body: z.string().describe("The content of the note or reply"),
+  created_at: z.string().optional().describe("Date the note was created at (ISO 8601 format)"),
+});
+
 // API Operation Parameter Schemas
 
 export const CreateOrUpdateFileSchema = ProjectParamsSchema.extend({
@@ -1085,6 +1101,8 @@ export type GitLabMergeRequestDiff = z.infer<
 export type CreateNoteOptions = z.infer<typeof CreateNoteSchema>;
 export type GitLabIssueLink = z.infer<typeof GitLabIssueLinkSchema>;
 export type ListIssueDiscussionsOptions = z.infer<typeof ListIssueDiscussionsSchema>;
+export type UpdateIssueNoteOptions = z.infer<typeof UpdateIssueNoteSchema>;
+export type CreateIssueNoteOptions = z.infer<typeof CreateIssueNoteSchema>;
 export type GitLabNamespace = z.infer<typeof GitLabNamespaceSchema>;
 export type GitLabNamespaceExistsResponse = z.infer<
   typeof GitLabNamespaceExistsResponseSchema