Background Obsessional slowness (OS) denotes a rare condition of disablingly slow motor performance. It was originally described in patients with obsessive‐compulsive disorder as a “primary” condition; however, subsequent reports have included heterogeneous clinical populations. We wished to reassess patients with this diagnosis at our own institution and also revisit the literature to provide an overview of this condition. Methods Clinical documentation and videos of 3 patients diagnosed with OS in the National Hospital for Neurology and Neurosurgery (London, UK) were reviewed. One of the patients was clinically reappraised. A systematic review of published articles with sufficient clinical patient information was also conducted. Results Our 3 cases were male with symptom onset in adolescence or early adulthood. Motor slowness with poverty of movement and a history of obsessive‐compulsive symptoms were characteristic. Poor speech production, bizarre postures, mannerisms, echophenomena, and oculogyric tics were also noted. Dopaminergic imaging was normal in 2 cases. One case had autistic features. Systematic literature review identified 77 further cases. Male preponderance with symptom onset mainly during the second decade and presence of obsessive‐compulsive symptoms were noted. Additional motor and neuropsychiatric features were often present. Conclusion The existence of OS as a “primary” condition is doubtful. This diagnosis has been given to characterize different clinical presentations ranging from obsessive‐compulsive disorder with motor slowness resulting from covert obsessive‐compulsive symptoms to catatonia. Clinicians should be aware of this syndrome to separate it from juvenile parkinsonism and other causes of motor slowness given that diagnostic approaches and treatment strategies differ.