An apparatus and method are described for a multithreaded-aware performance monitor of a processor. For example, one embodiment of a processor comprises: one or more simultaneous multithreading cores to simultaneously execute multiple instruction threads; a plurality of performance monitor counters, each performance monitor counter to count baseline events during processing of the multiple instruction threads; and a performance monitor circuit to determine whether multiple threads are concurrently generating the same baseline event and, if so, then the performance monitor circuit to distribute the count of the baseline event for only one of the multiple threads in each processor cycle for which the multiple threads are active and the baseline event applies to.