Background: Although suicide prevention programs have been shown to change suicide-related knowledge and attitudes, relatively little is known about their effects on actual behavior. Aims: Therefore, the focus of the present study was on improving participating school staff's practical and communication skills. Method: Suicide prevention workshops for students in grades 8-10 (N = 200) and a gatekeeper training program for school staff (N = 150) were conducted in 12 secondary schools in Germany. Schools were alternately assigned to one of three interventions (staff, students, or both trained) or to a waitlist control group. Results: School staff undergoing the training showed increased action-related knowledge, greater self-efficacy when counseling students in need and augmented counseling skills, and also had more conversations with students in need. Although students participating in the workshops did not seek help more frequently, they provided help to their peers more often in the conditions in which both students and school staff or only the latter had been trained. Limitations: The generalizability of the results is constrained by high dropout rates due to the COVID-19 pandemic and the relatively small sample size. Conclusion: A combination of suicide prevention programs for school staff and students appears to be most effective.