Introduction Worldwide, annually more than 800,000 suicides occur. In the Netherlands, suicide rates rose from 8.6 per 100,000 in 2007 to 11.4 per 100,000 in 2016. Rates in the province of Noord-Brabant were consistently higher than the national average. Noord-Brabant is a province in the south of the Netherlands covering an area of over 4700 km2 with 2.5 million inhabitants. Although Noord-Brabant has five specialised mental healthcare institutions (SMHIs), and 90% of suicides are deemed related to mental disorders, 60% of those who died by suicide did not receive mental health treatment. However, with good access to treatment, suicide could be preventable. Objectives To evaluate whether the systems intervention compared to the regular care approach led to a reduction in suicides in Noord-Brabant. We aimed to attain a reduction in suicides of at least 20%. Methods Co-design and development of a digital monitoring system and decision aid. Stepwise implementation per subregion of the systems intervention by the five specialized mental healthcare institutions (SMHIs) and their chain partners. Pre-post analysis for the whole province (Exact Rate Ratio Test, Poisson count). Results The SUPREMOCOL systems intervention consisted of four pillars, which were all supported by a digital decision aid and monitoring system. This was provided via a desktop computer with a secured login. The data were kept on a secured encrypted server. The number of professionals accessing the system was limited to two per SMHI or other chain partner. They could only see patients in their subregion, not in the whole of the province. The pillars of our systems intervention for suicide prevention are: 1. Swift identication of people at risk for suicide by triage on the spot after a non-fatal suicide attempt. 2. Provision of swift access to specialised mental health care for those at risk 3. Accommodating transitions in care following a collaborative care approach 4. Prevention of suicidal attempts after discharge or treatment dropout by 12 ...