Background: Clozapine is the most effective antipsychotic in treatment-resistant schizophrenia but its use portends with a high burden of adverse reactions. One adverse event reported both in case reports and cross-sectional surveys is the emergence or worsening of obsessive compulsive symptoms (OCS). Objectives: This study presents a retrospective review of a UK cohort of clozapine-treated individuals with the aim to further investigate the complex relationship between clozapine and OCS. Methods: An extensive review of the medical records of 49 patients receiving clozapine in the Southampton area was undertaken. We searched for a diagnosis of obsessive compulsive disorder, signs or symptoms of obsessive compulsive disorder or the prescribing of selected antidepressants the year before clozapine initiation and the year after. Results: Fifteen patients (31%) had reports of OCS during the 2-year data collection period. Twelve patients (24%) had OCS before clozapine initiation while only 7 (14%) had symptoms after clozapine was initiated. De novo OCS were reported in three (6%) cases after 5–9 months of clozapine treatment. Conclusions: As with previous studies it was not possible to establish a definitive link between clozapine and OCS. Clinicians should be mindful of the common comorbidity of OCS and schizophrenia and the possible increased risk incurred when starting clozapine.