The vast majority of suicides occur in low-and middle-income countries (LMICs), and evidence on effective psychotherapeutic interventions to prevent suicide that are culturally adapted to these contexts is limited. This scenario implies an urgent need for evidence-based suicide prevention strategies in Brazil. This research aims to evaluate the effectiveness of brief cognitive-behavioral therapy in preventing suicide in an outpatient setting of a Brazilian university. A randomized, controlled clinical trial with two arms, whose participants are adults who have attempted suicide or have had suicidal ideation with intent to die, will be designed. Inclusion criteria will be suicidal ideation with intent to die in the last week and/or suicide attempt in the last month. Patients will be randomly assigned to receive either a weekly 12-session supportive therapy or brief cognitive-behavioral therapy. The duration of treatment will be approximately 3 months. Both groups will have weekly individual therapy. Follow-up contact will be made 1 month and 6 months after treatment. If necessary, patients are entitled to two booster sessions during the follow-up period. The outcomes to be assessed, a priori, are suicide attempts, self-harm without suicidal intent and suicidal ideation, assessed by the Beck Scale for Suicide Ideation (BSI). Linear mixed models will be used to assess the outcomes of continuous variables, logistic regression models for categorical outcomes and survival analysis for the analysis of suicide attempts.