diff --git a/datastructure/set/set.go b/datastructure/set/set.go
index 4b351e7..17f37bd 100644
--- a/datastructure/set/set.go
+++ b/datastructure/set/set.go
@@ -17,6 +17,19 @@ func (s Set[T]) Add(values ...T) {
 	}
 }
 
+// AddIfNotExist checks if item exists in the set,
+// it adds the item to set and returns true if it does not exist in the set,
+// or else it does nothing and returns false.
+func (s Set[T]) AddIfNotExist(value T) bool {
+	if !s.Contain(value) {
+		if _, ok := s[value]; !ok {
+			s[value] = struct{}{}
+			return true
+		}
+	}
+	return false
+}
+
 // Contain checks if set contains value or not
 func (s Set[T]) Contain(value T) bool {
 	_, ok := s[value]
diff --git a/datastructure/set/set_test.go b/datastructure/set/set_test.go
index be11e68..b8067fc 100644
--- a/datastructure/set/set_test.go
+++ b/datastructure/set/set_test.go
@@ -17,6 +17,17 @@ func TestSet_Add(t *testing.T) {
 	assert.Equal(true, set.Equal(expected))
 }
 
+func TestSet_AddIfNotExist(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSet_AddIfNotExist")
+
+	set := NewSet[int]()
+	set.Add(1, 2, 3)
+
+	assert.Equal(false, set.AddIfNotExist(1))
+	assert.Equal(true, set.AddIfNotExist(4))
+	assert.Equal(NewSet(1, 2, 3, 4), set)
+}
+
 func TestSet_Contain(t *testing.T) {
 	assert := internal.NewAssert(t, "TestSet_Contain")