OBJECTIVES: As Flanders (Belgium) has an average suicide rate of 1.76 times that in the EU, prevention of suicide is important to counter the negative consequences that are associated with suicide and suicide attempts. The objective of this study was to evaluate the cost-effectiveness of ‘De Zelfmoordlijn’, a suicide prevention helpline in Flanders. METHODS: An age-, gender- and medium (chat or telephone)-dependent Markov model with a time horizon of 10 years and a 12-month cycle-length was developed in order to predict cumulative costs and QALYs (quality adjusted life years) in a high-risk population. Costs were taken from a societal perspective. The model consists of six transition states: the initial phase, first non-fatal attempt, non-fatal re-attempt, follow-up, fatal attempt and death of other causes. A scenario with the existence of the helpline was compared with a scenario without  its existence. The effect of the helpline was derived from published literature. Uncertainty was taken into account by carrying out one-way and probabilistic sensitivity analysis. RESULTS: Over a period of 10 years, it is estimated that 35% of suicides and suicide attempts can be avoided in this high-risk population, due to the suicide helpline. By means of the chat sessions and telephone service ‘De Zelfmoordlijn’ increased average QALYs respectively by 0.057(-0.029-0.143) and 0.099 (0.050-0.148) for men and by 0.034 (-0.015-0.081) due to the telephone service in women. The chat service led to a QALY neutral result in women (-0.002; -0.097-0.093). The total costs decreased, resulting in net societal savings in men of €2652 (€2094-€3521) for the chat service and €2010 (€1600-€2444) for the telephone service and in women of €1930 (€1408-€2489) and €1496 (€1116-€1910) respectively.  CONCLUSIONS: This modeling exercise predicts that ‘De Zelfmoordlijn’ is a cost-effective, net saving, intervention to prevent suicide in a high-risk population.