Acute-onset obsessive-compulsive disorder can be challenging, especially when triggered by an underlying disease process. Clinicians often turn to Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS), but it is important to consider a broad differential in these patients. We present a case of a 9-year-old girl with acute-onset obsessive-compulsive behavior likely triggered by a post-infectious phenomenon that ultimately resolved following treatment with plasmapheresis.