INTRODUCTION: Mental health professionals play an important role in helping patients at risk of suicide. Therefore, mental health professionals must acquire basic knowledge and skills in suicide prevention to support patients with suicidal behavior. However, not all mental health professionals have sufficient knowledge and skills, and educational programs for mental health professionals are rare. We previously developed a workshop covering 10 steps healthcare professionals must take to care for mentally ill patients (the 10 Essentials program), and we adapted it for suicide prevention. This study aimed to evaluate the 10 Essentials program's effectiveness in educating mental health professionals. METHODS: This was an intervention study (pre-post comparison test). The participants of the present study were the mental health professionals (psychiatrists, psychiatric nurses, mental health social workers, clinical psychologists, and occupational therapists) who took part in the 10 Essentials workshops we delivered to several communities in Japan. The Attitudes Toward Suicide Scale (ATTS) was administered to the participants pre- and post-training to assess changes in their attitudes toward suicide after participating in the program. RESULTS: We analyzed data from 264 participants who completed the questionnaires. Their ATTS scores at post-training were significantly higher (and therefore more favorable) in the following dimensions: "common occurrence" (p = 0.012), "unjustified behavior" (p <
0.0001), and "preventability/readiness to help" (p <
0.0001), compared with those at pretraining. The ATTS scores at post-training were significantly lower (and therefore more favorable) in "right to suicide" (p <
0.0001), "suicidal expression as a mere threat" (p <
0.0001), and "impulsiveness" (p <
0.0001) compared with pretraining scores. Attitudes toward suicide among the participants shifted in a favorable direction after the program. CONCLUSION: In this study, the 10 Essentials program was effective in improving attitudes toward suicide among mental health professionals. Their attitudes became more favorable for helping patients with suicidal behavior. Further study will be needed to examine participants with different backgrounds and the long-term effects of the training.