Provided is a messaging service system and method for adding a contact through a grouping operation. The messaging service system includes a member registering unit configured to create a group, and to register a first member designated by a user as a first participant of the group; and a member managing unit configured to disclose the group to the first participant of the group, to assign, to the first participant, a permission to add a second participant to the group, in which, the member registering unit is configured to add a second member designated by the first participant of the group as the second participant of the group, and the member managing unit is configured to display a list of members registered by the member registering unit and a list of groups created by the member registering unit.