This study reports the outcomes, during follow-up, of a low-cost postcard intervention in a Randomized Control Trial of hospital-treated self-poisoning (n=2300). The intervention was 9 postcards over 12 months (plus usual treatment) versus usual treatment. Three binary endpoints at 12-24 months (n=2001) were: any suicidal ideation, suicide attempt, or self-cutting. There was a significant reduction in any suicidal ideation (RRR 0.20 CI 95% 0.13-0.27), (NNT 8, 6-13), and any suicide attempt (RRR 0.31, 0.06-0.50), (NNT 35, 19-195), in this non-western population. However, there was no effect on self-cutting (RRR -0.01, -1.05-0.51). Sustained, brief contact by mail may reduce some forms of suicidal behavior in self-poisoning patients during the post intervention phase.