diff --git a/README.md b/README.md
index 91da9a7..0de3502 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,24 @@ python task.py list
 python task.py done 1
 ```
 
+### JSON Output
+
+All commands support a `--json` flag for machine-readable output:
+
+```bash
+# Add a task with JSON output
+python task.py add --json "Buy groceries"
+# {"success": true, "message": "Added task 1", "task": {"id": 1, "description": "Buy groceries", "done": false}}
+
+# List tasks in JSON format
+python task.py list --json
+# {"success": true, "tasks": [{"id": 1, "description": "Buy groceries", "done": false}]}
+
+# Mark done with JSON output
+python task.py done --json 1
+# {"success": true, "message": "Marked task 1 as done", "task": {"id": 1, "description": "Buy groceries", "done": true}}
+```
+
 ## Testing
 
 ```bash
diff --git a/commands/add.py b/commands/add.py
index 1b1a943..7a24a2e 100644
--- a/commands/add.py
+++ b/commands/add.py
@@ -19,7 +19,7 @@ def validate_description(description):
     return description.strip()
 
 
-def add_task(description):
+def add_task(description, json_output=False):
     """Add a new task."""
     description = validate_description(description)
 
@@ -31,7 +31,12 @@ def add_task(description):
         tasks = json.loads(tasks_file.read_text())
 
     task_id = len(tasks) + 1
-    tasks.append({"id": task_id, "description": description, "done": False})
+    task = {"id": task_id, "description": description, "done": False}
+    tasks.append(task)
 
     tasks_file.write_text(json.dumps(tasks, indent=2))
-    print(f"Added task {task_id}: {description}")
+
+    if json_output:
+        print(json.dumps({"success": True, "message": f"Added task {task_id}", "task": task}))
+    else:
+        print(f"Added task {task_id}: {description}")
diff --git a/commands/done.py b/commands/done.py
index c9dfd42..86e8040 100644
--- a/commands/done.py
+++ b/commands/done.py
@@ -17,11 +17,14 @@ def validate_task_id(tasks, task_id):
     return task_id
 
 
-def mark_done(task_id):
+def mark_done(task_id, json_output=False):
     """Mark a task as complete."""
     tasks_file = get_tasks_file()
     if not tasks_file.exists():
-        print("No tasks found!")
+        if json_output:
+            print(json.dumps({"success": False, "message": "No tasks found"}))
+        else:
+            print("No tasks found!")
         return
 
     tasks = json.loads(tasks_file.read_text())
@@ -31,7 +34,13 @@ def mark_done(task_id):
         if task["id"] == task_id:
             task["done"] = True
             tasks_file.write_text(json.dumps(tasks, indent=2))
-            print(f"Marked task {task_id} as done: {task['description']}")
+            if json_output:
+                print(json.dumps({"success": True, "message": f"Marked task {task_id} as done", "task": task}))
+            else:
+                print(f"Marked task {task_id} as done: {task['description']}")
             return
 
-    print(f"Task {task_id} not found")
+    if json_output:
+        print(json.dumps({"success": False, "message": f"Task {task_id} not found"}))
+    else:
+        print(f"Task {task_id} not found")
diff --git a/commands/list.py b/commands/list.py
index 714315d..ad8e378 100644
--- a/commands/list.py
+++ b/commands/list.py
@@ -18,20 +18,28 @@ def validate_task_file():
     return tasks_file
 
 
-def list_tasks():
+def list_tasks(json_output=False):
     """List all tasks."""
-    # NOTE: No --json flag support yet (feature bounty)
     tasks_file = validate_task_file()
     if not tasks_file:
-        print("No tasks yet!")
+        if json_output:
+            print(json.dumps({"success": True, "tasks": []}))
+        else:
+            print("No tasks yet!")
         return
 
     tasks = json.loads(tasks_file.read_text())
 
     if not tasks:
-        print("No tasks yet!")
+        if json_output:
+            print(json.dumps({"success": True, "tasks": []}))
+        else:
+            print("No tasks yet!")
         return
 
-    for task in tasks:
-        status = "✓" if task["done"] else " "
-        print(f"[{status}] {task['id']}. {task['description']}")
+    if json_output:
+        print(json.dumps({"success": True, "tasks": tasks}))
+    else:
+        for task in tasks:
+            status = "✓" if task["done"] else " "
+            print(f"[{status}] {task['id']}. {task['description']}")
diff --git a/task.py b/task.py
index 53cc8ed..745e401 100644
--- a/task.py
+++ b/task.py
@@ -25,22 +25,25 @@ def main():
     # Add command
     add_parser = subparsers.add_parser("add", help="Add a new task")
     add_parser.add_argument("description", help="Task description")
+    add_parser.add_argument("--json", action="store_true", help="Output in JSON format")
 
     # List command
     list_parser = subparsers.add_parser("list", help="List all tasks")
+    list_parser.add_argument("--json", action="store_true", help="Output in JSON format")
 
     # Done command
     done_parser = subparsers.add_parser("done", help="Mark task as complete")
     done_parser.add_argument("task_id", type=int, help="Task ID to mark done")
+    done_parser.add_argument("--json", action="store_true", help="Output in JSON format")
 
     args = parser.parse_args()
 
     if args.command == "add":
-        add_task(args.description)
+        add_task(args.description, json_output=args.json)
     elif args.command == "list":
-        list_tasks()
+        list_tasks(json_output=args.json)
     elif args.command == "done":
-        mark_done(args.task_id)
+        mark_done(args.task_id, json_output=args.json)
     else:
         parser.print_help()
 
diff --git a/test_task.py b/test_task.py
index ba98e43..151f5d7 100644
--- a/test_task.py
+++ b/test_task.py
@@ -2,9 +2,11 @@
 
 import json
 import pytest
+import subprocess
 from pathlib import Path
 from commands.add import add_task, validate_description
-from commands.done import validate_task_id
+from commands.list import list_tasks
+from commands.done import validate_task_id, mark_done
 
 
 def test_validate_description():
@@ -28,3 +30,84 @@ def test_validate_task_id():
 
     with pytest.raises(ValueError):
         validate_task_id(tasks, 99)
+
+
+# ── JSON output tests ─────────────────────────────────────────────────────
+
+
+def test_add_json_output(capsys, tmp_path, monkeypatch):
+    """Test add command with --json flag produces valid JSON."""
+    monkeypatch.setattr(
+        "commands.add.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    add_task("Test task", json_output=True)
+    output = json.loads(capsys.readouterr().out)
+    assert output["success"] is True
+    assert output["task"]["description"] == "Test task"
+    assert output["task"]["id"] == 1
+    assert output["task"]["done"] is False
+
+
+def test_add_text_output(capsys, tmp_path, monkeypatch):
+    """Test add command without --json flag produces plain text."""
+    monkeypatch.setattr(
+        "commands.add.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    add_task("Test task", json_output=False)
+    output = capsys.readouterr().out.strip()
+    assert "Added task 1: Test task" == output
+
+
+def test_list_json_output(capsys, tmp_path, monkeypatch):
+    """Test list command with --json flag produces valid JSON."""
+    monkeypatch.setattr(
+        "commands.add.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    monkeypatch.setattr(
+        "commands.list.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    add_task("Task one")
+    add_task("Task two")
+    list_tasks(json_output=True)
+    output = json.loads(capsys.readouterr().out.strip().split("\n")[-1])
+    assert output["success"] is True
+    assert len(output["tasks"]) == 2
+    assert output["tasks"][0]["description"] == "Task one"
+
+
+def test_list_empty_json(capsys, tmp_path, monkeypatch):
+    """Test list --json with no tasks returns empty array."""
+    monkeypatch.setattr(
+        "commands.list.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    list_tasks(json_output=True)
+    output = json.loads(capsys.readouterr().out)
+    assert output["success"] is True
+    assert output["tasks"] == []
+
+
+def test_done_json_output(capsys, tmp_path, monkeypatch):
+    """Test done command with --json flag produces valid JSON."""
+    monkeypatch.setattr(
+        "commands.add.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    monkeypatch.setattr(
+        "commands.done.get_tasks_file", lambda: tmp_path / "tasks.json"
+    )
+    add_task("Task to complete")
+    mark_done(1, json_output=True)
+    lines = capsys.readouterr().out.strip().split("\n")
+    output = json.loads(lines[-1])
+    assert output["success"] is True
+    assert output["task"]["done"] is True
+
+
+def test_cli_json_flag():
+    """Test --json flag works via CLI invocation."""
+    result = subprocess.run(
+        ["python3", "task.py", "list", "--json"],
+        capture_output=True, text=True, cwd=str(Path(__file__).parent),
+    )
+    output = json.loads(result.stdout)
+    assert "success" in output
+    assert "tasks" in output