OBJECTIVE: We evaluated the effect of a digitally supported systems intervention for suicide prevention (SUPREMOCOL) in Noord-Brabant, the Netherlands. METHOD: Non-randomized stepped wedge trial design (SWTD). Stepwise implementation in the five subregions of the systems intervention. Pre-post analysis for the whole province (Exact Rate Ratio Test, Poisson count). SWTD Hazard Ratios of suicides per person-years for subregional analysis of control versus intervention conditions over five times three months. Sensitivity analysis. RESULTS: Suicide rates dropped 17.8% (p = .013) from 14.4 suicides per 100,000 before the start of implementation of the systems intervention (2017), to 11.9 (2018) and 11.8 (2019) per 100, during implementation; a significant reduction (p = .043) compared to no changes in the rest of the Netherlands. Suicide rates dropped further by 21.5% (p = .002) to 11.3 suicides per 100,000 during sustained implementation in 2021. Sensitivity analysis confirmed the reduction (p = .02). The SWTD analysis over 15 months in 2018–2019 did not show a significant association of this reduction with implementation per subregional level, probably due to insufficient power given the short SWTD timeframe for implementation and low suicide rates per subregion. CONCLUSIONS: During the SUPREMOCOL systems intervention, over four years, there was a sustained and significant reduction of suicides in Noord-Brabant.