Background: Approximately half of patients who attempt or die by suicide screened negative for suicidal ideation during their most recent medical visit. Maladaptive beliefs and schemas can increase cognitive vulnerability to suicidal behavior, even among patients without recent or past suicidal thoughts and behaviors. Assessing these beliefs could improve the detection of patients who will engage in suicidal behavior after screening negative for elevated suicide risk. Methods: Primary care patients who completed the Patient Health Questionnaire-9 and the Suicide Cognitions Scale-Revised (SCS-R) during routine clinic visits and denied suicidal ideation at baseline (N = 2417) were included in the study sample. Suicidal behaviors during the 12 months after baseline were assessed. Logistic regression analyses examined the association of baseline SCS-R scores with later suicidal behavior. Results: In both univariate and multivariate analyses, SCS-R total scores were associated with significantly increased risk of suicidal behavior within 90, 180, and 365 days post-baseline. Results were unchanged when patients who reported prior suicidal behavior were excluded (N = 2178). In item-level analyses, all 16 SCS-R items significantly differentiated patients with and without follow-up suicidal behavior. Limitations: Study limitations included missing follow-up data, restriction of sample to U.S. military medical beneficiaries, and inability to assess representativeness of the sample relative to the full primary care population. Conclusions: SCS-R scores are elevated among patients who attempt suicide after denying both suicidal ideation and prior suicide attempts, suggesting the scale may reflect enduring suicide risk. The SCS-R could enhance suicide risk screening and assessment.