diff --git a/pkg/models/task_duplicate.go b/pkg/models/task_duplicate.go
new file mode 100644
index 000000000..6be9bbec1
--- /dev/null
+++ b/pkg/models/task_duplicate.go
@@ -0,0 +1,172 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package models
+
+import (
+	"code.vikunja.io/api/pkg/files"
+	"code.vikunja.io/api/pkg/log"
+	"code.vikunja.io/api/pkg/web"
+
+	"xorm.io/xorm"
+)
+
+// TaskDuplicate holds everything needed to duplicate a task
+type TaskDuplicate struct {
+	// The task id of the task to duplicate
+	TaskID int64 `json:"-" param:"projecttask"`
+
+	// The duplicated task
+	Task *Task `json:"duplicated_task,omitempty"`
+
+	web.Permissions `json:"-"`
+	web.CRUDable    `json:"-"`
+}
+
+// CanCreate checks if a user has the permission to duplicate a task
+func (td *TaskDuplicate) CanCreate(s *xorm.Session, a web.Auth) (canCreate bool, err error) {
+	// Need read access on the original task
+	originalTask := &Task{ID: td.TaskID}
+	canRead, _, err := originalTask.CanRead(s, a)
+	if err != nil || !canRead {
+		return canRead, err
+	}
+
+	// Need write access on the project to create tasks in it
+	p := &Project{ID: originalTask.ProjectID}
+	return p.CanUpdate(s, a)
+}
+
+// Create duplicates a task
+// @Summary Duplicate a task
+// @Description Copies a task with all its properties (labels, assignees, attachments, reminders) into the same project. Creates a "copied from" relation between the new and original task.
+// @tags task
+// @Accept json
+// @Produce json
+// @Security JWTKeyAuth
+// @Param taskID path int true "The task ID to duplicate"
+// @Success 201 {object} models.TaskDuplicate "The duplicated task."
+// @Failure 403 {object} web.HTTPError "The user does not have access to the task."
+// @Failure 500 {object} models.Message "Internal error"
+// @Router /tasks/{taskID}/duplicate [put]
+func (td *TaskDuplicate) Create(s *xorm.Session, doer web.Auth) (err error) {
+	// Get the original task with all details
+	originalTask := &Task{ID: td.TaskID}
+	err = originalTask.ReadOne(s, doer)
+	if err != nil {
+		return err
+	}
+
+	log.Debugf("Duplicating task %d", td.TaskID)
+
+	// Create the new task
+	newTask := &Task{
+		Title:       originalTask.Title,
+		Description: originalTask.Description,
+		Done:        false,
+		DueDate:     originalTask.DueDate,
+		ProjectID:   originalTask.ProjectID,
+		RepeatAfter: originalTask.RepeatAfter,
+		RepeatMode:  originalTask.RepeatMode,
+		Priority:    originalTask.Priority,
+		StartDate:   originalTask.StartDate,
+		EndDate:     originalTask.EndDate,
+		HexColor:    originalTask.HexColor,
+		PercentDone: originalTask.PercentDone,
+		Assignees:   originalTask.Assignees,
+		Reminders:   originalTask.Reminders,
+	}
+
+	err = createTask(s, newTask, doer, true, true)
+	if err != nil {
+		return err
+	}
+
+	log.Debugf("Duplicated task %d into new task %d", td.TaskID, newTask.ID)
+
+	// Duplicate labels
+	labelTasks := []*LabelTask{}
+	err = s.Where("task_id = ?", td.TaskID).Find(&labelTasks)
+	if err != nil {
+		return err
+	}
+	for _, lt := range labelTasks {
+		lt.ID = 0
+		lt.TaskID = newTask.ID
+		if _, err := s.Insert(lt); err != nil {
+			return err
+		}
+	}
+
+	log.Debugf("Duplicated labels from task %d into %d", td.TaskID, newTask.ID)
+
+	// Duplicate attachments (copy underlying files)
+	attachments, err := getTaskAttachmentsByTaskIDs(s, []int64{td.TaskID})
+	if err != nil {
+		return err
+	}
+	for _, attachment := range attachments {
+		attachment.ID = 0
+		attachment.TaskID = newTask.ID
+		attachment.File = &files.File{ID: attachment.FileID}
+		if err := attachment.File.LoadFileMetaByID(); err != nil {
+			if files.IsErrFileDoesNotExist(err) {
+				log.Debugf("Not duplicating attachment (file %d) because it does not exist", attachment.FileID)
+				continue
+			}
+			return err
+		}
+		if err := attachment.File.LoadFileByID(); err != nil {
+			return err
+		}
+
+		err := attachment.NewAttachment(s, attachment.File.File, attachment.File.Name, attachment.File.Size, doer)
+		if err != nil {
+			return err
+		}
+		if attachment.File.File != nil {
+			_ = attachment.File.File.Close()
+		}
+	}
+
+	log.Debugf("Duplicated attachments from task %d into %d", td.TaskID, newTask.ID)
+
+	// Create "copied from/to" relation
+	rel := &TaskRelation{
+		TaskID:       newTask.ID,
+		OtherTaskID:  td.TaskID,
+		RelationKind: RelationKindCopiedFrom,
+		CreatedByID:  doer.GetID(),
+	}
+	if _, err := s.Insert(rel); err != nil {
+		return err
+	}
+	reverseRel := &TaskRelation{
+		TaskID:       td.TaskID,
+		OtherTaskID:  newTask.ID,
+		RelationKind: RelationKindCopiedTo,
+		CreatedByID:  doer.GetID(),
+	}
+	if _, err := s.Insert(reverseRel); err != nil {
+		return err
+	}
+
+	log.Debugf("Created copy relations between task %d and %d", td.TaskID, newTask.ID)
+
+	// Re-read the task to populate all fields for the response
+	td.Task = newTask
+	return td.Task.ReadOne(s, doer)
+}
diff --git a/pkg/models/task_duplicate_test.go b/pkg/models/task_duplicate_test.go
new file mode 100644
index 000000000..4435af873
--- /dev/null
+++ b/pkg/models/task_duplicate_test.go
@@ -0,0 +1,89 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package models
+
+import (
+	"testing"
+
+	"code.vikunja.io/api/pkg/db"
+	"code.vikunja.io/api/pkg/files"
+	"code.vikunja.io/api/pkg/user"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTaskDuplicate(t *testing.T) {
+	t.Run("basic duplicate", func(t *testing.T) {
+		files.InitTestFileFixtures(t)
+		db.LoadAndAssertFixtures(t)
+		s := db.NewSession()
+		defer s.Close()
+
+		u := &user.User{ID: 1}
+
+		td := &TaskDuplicate{
+			TaskID: 1,
+		}
+		can, err := td.CanCreate(s, u)
+		require.NoError(t, err)
+		assert.True(t, can)
+		err = td.Create(s, u)
+		require.NoError(t, err)
+		assert.NotEqual(t, int64(0), td.Task.ID)
+		assert.NotEqual(t, int64(1), td.Task.ID)
+		assert.Equal(t, "task #1", td.Task.Title)
+
+		// Verify labels were copied
+		labelCount, err := s.Where("task_id = ?", td.Task.ID).Count(&LabelTask{})
+		require.NoError(t, err)
+		originalLabelCount, err := s.Where("task_id = ?", int64(1)).Count(&LabelTask{})
+		require.NoError(t, err)
+		assert.Equal(t, originalLabelCount, labelCount)
+
+		// Verify assignees were copied
+		assigneeCount, err := s.Where("task_id = ?", td.Task.ID).Count(&TaskAssginee{})
+		require.NoError(t, err)
+		originalAssigneeCount, err := s.Where("task_id = ?", int64(1)).Count(&TaskAssginee{})
+		require.NoError(t, err)
+		assert.Equal(t, originalAssigneeCount, assigneeCount)
+
+		// Verify a "copiedfrom" relation was created
+		relationCount, err := s.
+			Where("task_id = ? AND other_task_id = ? AND relation_kind = ?",
+				td.Task.ID, int64(1), RelationKindCopiedFrom).
+			Count(&TaskRelation{})
+		require.NoError(t, err)
+		assert.Equal(t, int64(1), relationCount)
+	})
+
+	t.Run("no permission", func(t *testing.T) {
+		db.LoadAndAssertFixtures(t)
+		s := db.NewSession()
+		defer s.Close()
+
+		// User 2 does not have write access to task 1's project (project 1)
+		u := &user.User{ID: 2}
+
+		td := &TaskDuplicate{
+			TaskID: 1,
+		}
+		can, err := td.CanCreate(s, u)
+		require.NoError(t, err)
+		assert.False(t, can)
+	})
+}