diff --git a/asynq.go b/asynq.go
index cda9a23..3d27d06 100644
--- a/asynq.go
+++ b/asynq.go
@@ -162,6 +162,8 @@ func newTaskInfo(msg *base.TaskMessage, state base.TaskState, nextProcessAt time
 		info.State = TaskStateArchived
 	case base.TaskStateCompleted:
 		info.State = TaskStateCompleted
+	case base.TaskStateAggregating:
+		info.State = TaskStateAggregating
 	default:
 		panic(fmt.Sprintf("internal error: unknown state: %d", state))
 	}
@@ -189,6 +191,9 @@ const (
 
 	// Indicates that the task is processed successfully and retained until the retention TTL expires.
 	TaskStateCompleted
+
+	// Indicates that the task is waiting in a group to be aggreated into one task.
+	TaskStateAggregating
 )
 
 func (s TaskState) String() string {
@@ -205,6 +210,8 @@ func (s TaskState) String() string {
 		return "archived"
 	case TaskStateCompleted:
 		return "completed"
+	case TaskStateAggregating:
+		return "aggregating"
 	}
 	panic("asynq: unknown task state")
 }
diff --git a/client.go b/client.go
index 7c4e259..34aafd5 100644
--- a/client.go
+++ b/client.go
@@ -227,6 +227,7 @@ type option struct {
 	uniqueTTL time.Duration
 	processAt time.Time
 	retention time.Duration
+	groupKey  string
 }
 
 // composeOptions merges user provided options into the default options
@@ -254,8 +255,8 @@ func composeOptions(opts ...Option) (option, error) {
 			res.queue = qname
 		case taskIDOption:
 			id := string(opt)
-			if err := validateTaskID(id); err != nil {
-				return option{}, err
+			if isBlank(id) {
+				return option{}, errors.New("task ID cannot be empty")
 			}
 			res.taskID = id
 		case timeoutOption:
@@ -274,6 +275,12 @@ func composeOptions(opts ...Option) (option, error) {
 			res.processAt = time.Now().Add(time.Duration(opt))
 		case retentionOption:
 			res.retention = time.Duration(opt)
+		case groupOption:
+			key := string(opt)
+			if isBlank(key) {
+				return option{}, errors.New("group key cannot be empty")
+			}
+			res.groupKey = key
 		default:
 			// ignore unexpected option
 		}
@@ -281,12 +288,9 @@ func composeOptions(opts ...Option) (option, error) {
 	return res, nil
 }
 
-// validates user provided task ID string.
-func validateTaskID(id string) error {
-	if strings.TrimSpace(id) == "" {
-		return errors.New("task ID cannot be empty")
-	}
-	return nil
+// isBlank returns true if the given s is empty or consist of all whitespaces.
+func isBlank(s string) bool {
+	return strings.TrimSpace(s) == ""
 }
 
 const (
@@ -375,13 +379,18 @@ func (c *Client) EnqueueContext(ctx context.Context, task *Task, opts ...Option)
 	}
 	now := time.Now()
 	var state base.TaskState
-	if opt.processAt.Before(now) || opt.processAt.Equal(now) {
+	if opt.processAt.After(now) {
+		err = c.schedule(ctx, msg, opt.processAt, opt.uniqueTTL)
+		state = base.TaskStateScheduled
+	} else if opt.groupKey != "" {
+		// Use zero value for processAt since we don't know when the task will be aggregated and processed.
+		opt.processAt = time.Time{}
+		err = c.addToGroup(ctx, msg, opt.groupKey, opt.uniqueTTL)
+		state = base.TaskStateAggregating
+	} else {
 		opt.processAt = now
 		err = c.enqueue(ctx, msg, opt.uniqueTTL)
 		state = base.TaskStatePending
-	} else {
-		err = c.schedule(ctx, msg, opt.processAt, opt.uniqueTTL)
-		state = base.TaskStateScheduled
 	}
 	switch {
 	case errors.Is(err, errors.ErrDuplicateTask):
@@ -408,3 +417,10 @@ func (c *Client) schedule(ctx context.Context, msg *base.TaskMessage, t time.Tim
 	}
 	return c.rdb.Schedule(ctx, msg, t)
 }
+
+func (c *Client) addToGroup(ctx context.Context, msg *base.TaskMessage, groupKey string, uniqueTTL time.Duration) error {
+	if uniqueTTL > 0 {
+		return c.rdb.AddToGroupUnique(ctx, msg, groupKey, uniqueTTL)
+	}
+	return c.rdb.AddToGroup(ctx, msg, groupKey)
+}
diff --git a/client_test.go b/client_test.go
index 867de91..06cfec5 100644
--- a/client_test.go
+++ b/client_test.go
@@ -478,6 +478,154 @@ func TestClientEnqueue(t *testing.T) {
 	}
 }
 
+func TestClientEnqueueWithGroupOption(t *testing.T) {
+	r := setup(t)
+	client := NewClient(getRedisConnOpt(t))
+	defer client.Close()
+
+	task := NewTask("mytask", []byte("foo"))
+	now := time.Now()
+
+	tests := []struct {
+		desc          string
+		task          *Task
+		opts          []Option
+		wantInfo      *TaskInfo
+		wantPending   map[string][]*base.TaskMessage
+		wantGroups    map[string]map[string][]base.Z // map queue name to a set of groups
+		wantScheduled map[string][]base.Z
+	}{
+		{
+			desc: "With only Group option",
+			task: task,
+			opts: []Option{
+				Group("mygroup"),
+			},
+			wantInfo: &TaskInfo{
+				Queue:         "default",
+				Type:          task.Type(),
+				Payload:       task.Payload(),
+				State:         TaskStateAggregating,
+				MaxRetry:      defaultMaxRetry,
+				Retried:       0,
+				LastErr:       "",
+				LastFailedAt:  time.Time{},
+				Timeout:       defaultTimeout,
+				Deadline:      time.Time{},
+				NextProcessAt: time.Time{},
+			},
+			wantPending: map[string][]*base.TaskMessage{
+				"default": {}, // should not be pending
+			},
+			wantGroups: map[string]map[string][]base.Z{
+				"default": {
+					"mygroup": {
+						{
+							Message: &base.TaskMessage{
+								Type:     task.Type(),
+								Payload:  task.Payload(),
+								Retry:    defaultMaxRetry,
+								Queue:    "default",
+								Timeout:  int64(defaultTimeout.Seconds()),
+								Deadline: noDeadline.Unix(),
+							},
+							Score: now.Unix(),
+						},
+					},
+				},
+			},
+			wantScheduled: map[string][]base.Z{
+				"default": {},
+			},
+		},
+		{
+			desc: "With Group and ProcessIn options",
+			task: task,
+			opts: []Option{
+				Group("mygroup"),
+				ProcessIn(30 * time.Minute),
+			},
+			wantInfo: &TaskInfo{
+				Queue:         "default",
+				Type:          task.Type(),
+				Payload:       task.Payload(),
+				State:         TaskStateScheduled,
+				MaxRetry:      defaultMaxRetry,
+				Retried:       0,
+				LastErr:       "",
+				LastFailedAt:  time.Time{},
+				Timeout:       defaultTimeout,
+				Deadline:      time.Time{},
+				NextProcessAt: now.Add(30 * time.Minute),
+			},
+			wantPending: map[string][]*base.TaskMessage{
+				"default": {}, // should not be pending
+			},
+			wantGroups: map[string]map[string][]base.Z{
+				"default": {
+					"mygroup": {}, // should not be added to the group yet
+				},
+			},
+			wantScheduled: map[string][]base.Z{
+				"default": {
+					{
+						Message: &base.TaskMessage{
+							Type:     task.Type(),
+							Payload:  task.Payload(),
+							Retry:    defaultMaxRetry,
+							Queue:    "default",
+							Timeout:  int64(defaultTimeout.Seconds()),
+							Deadline: noDeadline.Unix(),
+						},
+						Score: now.Add(30 * time.Minute).Unix(),
+					},
+				},
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		h.FlushDB(t, r) // clean up db before each test case.
+
+		gotInfo, err := client.Enqueue(tc.task, tc.opts...)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		cmpOptions := []cmp.Option{
+			cmpopts.IgnoreFields(TaskInfo{}, "ID"),
+			cmpopts.EquateApproxTime(500 * time.Millisecond),
+		}
+		if diff := cmp.Diff(tc.wantInfo, gotInfo, cmpOptions...); diff != "" {
+			t.Errorf("%s;\nEnqueue(task) returned %v, want %v; (-want,+got)\n%s",
+				tc.desc, gotInfo, tc.wantInfo, diff)
+		}
+
+		for qname, want := range tc.wantPending {
+			got := h.GetPendingMessages(t, r, qname)
+			if diff := cmp.Diff(want, got, h.IgnoreIDOpt, cmpopts.EquateEmpty()); diff != "" {
+				t.Errorf("%s;\nmismatch found in %q; (-want,+got)\n%s", tc.desc, base.PendingKey(qname), diff)
+			}
+		}
+
+		for qname, groups := range tc.wantGroups {
+			for groupKey, want := range groups {
+				got := h.GetGroupEntries(t, r, qname, groupKey)
+				if diff := cmp.Diff(want, got, h.IgnoreIDOpt, cmpopts.EquateEmpty()); diff != "" {
+					t.Errorf("%s;\nmismatch found in %q; (-want,+got)\n%s", tc.desc, base.GroupKey(qname, groupKey), diff)
+				}
+			}
+		}
+
+		for qname, want := range tc.wantScheduled {
+			gotScheduled := h.GetScheduledEntries(t, r, qname)
+			if diff := cmp.Diff(want, gotScheduled, h.IgnoreIDOpt, cmpopts.EquateEmpty()); diff != "" {
+				t.Errorf("%s;\nmismatch found in %q; (-want,+got)\n%s", tc.desc, base.ScheduledKey(qname), diff)
+			}
+		}
+	}
+}
+
 func TestClientEnqueueWithTaskIDOption(t *testing.T) {
 	r := setup(t)
 	client := NewClient(getRedisConnOpt(t))
diff --git a/internal/asynqtest/asynqtest.go b/internal/asynqtest/asynqtest.go
index 46ea859..ce440e5 100644
--- a/internal/asynqtest/asynqtest.go
+++ b/internal/asynqtest/asynqtest.go
@@ -434,6 +434,14 @@ func GetCompletedEntries(tb testing.TB, r redis.UniversalClient, qname string) [
 	return getMessagesFromZSetWithScores(tb, r, qname, base.CompletedKey, base.TaskStateCompleted)
 }
 
+// GetGroupEntries returns all scheduled messages and its score in the given queue.
+// It also asserts the state field of the task.
+func GetGroupEntries(tb testing.TB, r redis.UniversalClient, qname, groupKey string) []base.Z {
+	tb.Helper()
+	return getMessagesFromZSetWithScores(tb, r, qname,
+		func(qname string) string { return base.GroupKey(qname, groupKey) }, base.TaskStateAggregating)
+}
+
 // Retrieves all messages stored under `keyFn(qname)` key in redis list.
 func getMessagesFromList(tb testing.TB, r redis.UniversalClient, qname string,
 	keyFn func(qname string) string, state base.TaskState) []*base.TaskMessage {
diff --git a/internal/base/base.go b/internal/base/base.go
index 98694ff..f43c316 100644
--- a/internal/base/base.go
+++ b/internal/base/base.go
@@ -50,6 +50,7 @@ const (
 	TaskStateRetry
 	TaskStateArchived
 	TaskStateCompleted
+	TaskStateAggregating // describes a state where task is waiting in a group to be aggregated
 )
 
 func (s TaskState) String() string {
@@ -66,6 +67,8 @@ func (s TaskState) String() string {
 		return "archived"
 	case TaskStateCompleted:
 		return "completed"
+	case TaskStateAggregating:
+		return "aggregating"
 	}
 	panic(fmt.Sprintf("internal error: unknown task state %d", s))
 }
@@ -84,6 +87,8 @@ func TaskStateFromString(s string) (TaskState, error) {
 		return TaskStateArchived, nil
 	case "completed":
 		return TaskStateCompleted, nil
+	case "aggregating":
+		return TaskStateAggregating, nil
 	}
 	return 0, errors.E(errors.FailedPrecondition, fmt.Sprintf("%q is not supported task state", s))
 }