Veterans receiving substance use disorder (SUD) treatment are at a clear elevated risk for engaging in suicidal behaviors. Intervening to reduce suicide risk during an episode of SUD treatment could meaningfully target a key high-risk group of Veterans. Cognitive Behavioral Therapy for Suicide Prevention (CBT-SP) was developed to reduce the frequency and duration of suicidal ideation, as well as decrease suicidal behaviors. The form of CBT-SP in this study progressed from building an understanding of the cognitive model to practicing new skills, and highlighted the links between substance use, craving, self-efficacy and suicidal ideation and attempts. CBT-SP was compared to an attention matched 8-session control condition (termed Supportive Psychoeducational Control [SPC]) during a multi-site randomized controlled trial for 299 Veterans receiving outpatient SUD treatment services within the Veterans Health Administration. The frequency of suicidal ideation remained relatively constant over 24-months of follow-up, however the duration of suicidal ideation decreased, and suicide attempts decreased relative to baseline in both conditions. Forty-two participants (14%) reported at least one suicide attempt during the 2-year follow-up period. No statistically significant differences were found between CBT-SP and SPC on any of these outcomes. Analyses of secondary outcomes indicate that preparatory behaviors for suicide were less common among those in the CBT-SP condition than SPC across the 24-month follow-up (OR, 95%CI = 0.44 (0.25, 0.79); p = 0.02). Veterans in SUD treatment are a high-risk group and delivery of suicide-specific interventions is feasible during SUD care. However, results did not indicate that CBT-SP was superior to SPC on any primary outcomes, underscoring the importance of identifying and testing alternative approaches that support suicide reduction in this group.