Background:Regulation of suicidal thoughts may be defined as a person's beliefs about their capacity to control affective and cognitive processes related to suicide. The inability to regulate suicidal thoughts is related to persistent suicidal thoughts, intentions, attempts, and suicide. Aims: The purpose of this study was to validate a scale that counselors could use to assess chat visitors' capacity to regulate suicidal thoughts. Method: The validity and reliability of the Regulation of Suicidal Thoughts Scale (RSTS) was evaluated using two different samples (n = 1,162, n = 241). Results: All items correlated with the theoretical construct regulation of suicidal thoughts, and the structural model showed the RSTS predicted perceived certainty to attempt suicide. Construct and criterion validity were inferred from a decrease in visitors' ability to control their thoughts of suicide from pre-chat to post-chat (Cohen's d = 91). Greater regulation in thoughts was also related to less certainty to attempt suicide. Limitations: Additional evidence is needed to validate the RSTS, especially among diverse populations. Conclusion: Counselors could use RSTS pre-chat scores to match counseling skills with specific affective and cognitive processes related to visitors' suicidal thoughts.