Objectives Obsessive-Compulsive Disorder (OCD) is a common co-morbid condition in schizophrenia, associated with poor prognosis. However, the prevalence of obsessive compulsive symptomatology (OCS) and its relationship to outcome has not been evaluated in adolescents at ultra high-risk for psychosis (UHR). Methods Sixty-four UHR and 26 non-prodromal comparison (NPC) youth were ascertained using the Structured Interview for Prodromal Syndromes (SIPS). Participants completed diagnostic interviews and the Padua Inventory (Sanavio, 1988), a self-report measure of OCS. Results UHR youth reported significantly higher rates of OCS on the Padua Inventory compared to NPC youth. Clinical diagnosis of OCD (20% of sample) was associated with lower risk of conversion to psychosis over the follow-up period, but was unrelated to clinical severity or psychosocial functioning. However, dimensional ratings of OCS were significantly associated with positive symptom severity, self-reported depression, and a trend toward increased suicidal ideation within the UHR sample. Conclusions OCS rates in UHR youth are well above estimated prevalence rates in normal populations, and commensurate with rates of comorbidity observed in schizophrenia. Although clinical diagnosis of OCD was not associated with later conversion to psychosis, OCS severity in UHR youth was associated with more acute symptomatic presentation, including more severe depression and suicidality.