Yes. But there are several restrictions you will need to be aware of. As a graduate student you need to register for graduate credits. Undergraduate credits, for example, do not count towards full time registration. The department facilitates taking undergraduate classes as graduate credits via a course designator CSE 587, where the student takes a core undergraduate class and get graduate credit for CSE 587. But you will need to do additional work relative to an undergraduate student taking the same class. Plus, you will get fewer credit (2 instead of 3). Finally, such CSE 587 may not count towards MS graduation unless specifically approved by the Graduate Director. For more details, see the Graduate Handbook.