Introduction Suicidal behaviour and deliberate self-harm are common among adults. Research indicates that maintaining contact either via letter or postcard with at-risk adults following discharge from care services can reduce reattempt risk. Feasibility trials demonstrated that intervention through text message was also acceptable to suicide attempters. Objective The aim of the current study is to investigate the effect of text message intervention versus traditional treatment on reducing the risk of suicide attempt repetition among adults after self-harm. Method The study will be a 2-year multicentric randomized controlled trial conducted by the Brest University Hospital, France. Participants will be adults discharged after self–harm, from emergency services or after a short hospitalization. The intervention is comprised of an SMS that will be sent at h48, D7, D15 and monthly during 6 month. The text message enquires about the patients’ well-being and includes information regarding individual sources of help and evidence-based self help strategies. As primary endpoint, we will assess the number of patients who reattempt suicide in each group at 6 months. As secondary endpoints, we will assess the number of patients who reattempt suicide at 13 month, suicidal behaviour at month 6 and 13 and Medical costs at month 13. Results Results will be accepted regarding the preliminary results of the study. Discussion This paper describes the design and deployment of a trial SIAM; an easily reproducible intervention that aims to reduce suicide risk in adults after self-harm. It utilizes several characteristics of interventions that have shown a significant reduction in the number of suicide reattempts.