The UML Collaboration diagram is used to model how objects involved in a scenario interact, with each object instantiating a particular class in the system. Objects are connected by links, each link representing an instance of an association between the respective classes involved. The link shows messages sent between the objects, and the type of message passed (synchronous, asynchronous, simple, balking, and timeout).

Collaboration diagrams offer a better view of a scenario than a Sequence diagram when the modeler is trying to understand all of the effects on a given object and are therefore good for procedural design.

Objects are depicted on a Collaboration diagram as rectangles. The object name is provided first, with the class name to the right; the two names are separated by a colon. To specify the multiple occurrence of an object by opening its definition dialog, click the Symbol tab, and then select Multiple. You can also select the Multiple Object tool from the toolbar.

Messages passed between objects are specified within the Link drawn between objects.

To add or edit messages for the link, right‑click it, and then click Associative, or select the link and then click Edit, Associative.

This is not the standard definition dialog that appears when you double-click the line (or choose Edit after right-clicking the line).

To synchronize a collaboration diagram with its partner sequence diagram at any time, see Synchronizing collaboration diagram with sequence diagram.