Objective <p>Previous research has established a strong association between obsessive-compulsive disorder (OCD) and elevated suicidality; however, the impact of the severity of obsessive-compulsive symptoms (OCSs) on suicidality and the mechanisms underlying this influence remain insufficiently understood. Impulsivity is a strongly predictive factor for suicidality and positively correlated with OCD. Based on self-control depletion theory and dual-regulation models, OCSs might increase suicidality via impulsivity. Therefore, the present study aims to explore their relationship and the potential mediating role of impulsivity.</p> Methods <p>A total of 10,754 college students were assessed through questionnaires, including the Symptom Checklist-90 (SCL-90) Obsessive-Compulsive Subscale, the Brief Barratt Impulsiveness Scale (BBIS), and the Suicide Behavioral Questionnaire-Revised (SBQ-R). Latent profile analysis was employed to classify participants into distinct groups, followed by a person-centered relative mediation analysis to validate the proposed model.</p> Results <p>Students were grouped into low OCSs, middle OCSs, and high OCSs. Using low OCSs as a reference, middle and high OCSs positively predicted impulsivity and suicidality, and the latter had a higher effect size. Impulsivity was a mediator as hypothesized.</p> Conclusions <p>Impulsivity is one of the reasons why OCSs enhance suicidality, and their relationship is increasingly strong when OCSs become severe.</p>