This retrospective case series describes the clinical features, treatment, and course of disease in 17 cats diagnosed with primary immune thrombocytopenia (pITP). At the time of diagnosis, median age was 4.25 yr (range 7 mo to 16 yr), 15 cats (88.2%) had clinical bleeding, and median platelet count was 10,000/μL (range 5000-50,000/μL). All 17 cats were treated with corticosteroids; cyclosporine was additionally prescribed in 14 cats. The median duration of immunosuppressive therapy was 365 days (range 49-2086 days). Thirteen cats achieved a platelet count > 100,000/µL at a median of 15 days (range 2-207 days) following diagnosis of pITP. Only one cat achieved a full remission. A relapse was documented in 10 cats (59%) at a median of 191 days (range 67-1022 days) after diagnosis and 48 days (range 15-196 days) after immunosuppressive medication was reduced or discontinued. Median survival time was 1067 days (range 49-2516 days). No patient, clinicopathological, or treatment variables were identified to affect 3 and 6 mo survival. This study highlights that clinical bleeding is common in cats with pITP, and despite an initial positive response to therapy, it can be difficult to maintain remission.