BackgroundSuicide is a major public health problem, especially among individuals over 50 years old. Despite the suitability of this life stage for prevention, research on the efficacy of psychological interventions is scarce and methodologically limited, affecting their clinical utility and efficacy. Brief, flexible interventions that can be applied both in-person and remotely are needed. This study aims to evaluate the efficacy of a brief problem-solving-based suicide prevention program applied through various modalities to individuals over 50 years old.MethodsA randomized controlled trial will be conducted. A sample of 212 adults aged 50 or older with suicidal ideation will be randomly assigned to a problem-solving-based psychological intervention administered face-to-face (PSPI-P; n = 53), by telephone multiconference (PSPI-M; n = 53), via a smartphone app (PSPI-A; n = 53), or to a usual care control group (UCCG; n = 53). The intervention will be delivered in 7 sessions or modules of 90 min each. Blind trained evaluators will conduct assessments at pre-intervention, post-intervention, and follow-ups at 3, 6, and 12 months. The primary outcome will be suicidal ideation evaluated using the Suicidal Ideation Scale (SSI) and the Columbia Suicide Severity Rating Scale (C-SSRS). Secondary outcomes will include hopelessness, anxiety and depression symptoms, reasons for living, impulsivity, problem-solving skills, social support, anger syndrome, gratitude, personality, dropouts, treatment adherence, and satisfaction with the intervention.DiscussionThis study will provide evidence of the efficacy of a brief problem-solving-based intervention for suicide prevention in individuals over 50 years old, administered face-to-face, by telephone multiconference, and via a smartphone app. If results are favorable, it will indicate that an effective, accessible, clinically and socially useful suicide prevention intervention has been developed for affected individuals, families, and communities.Trial registrationClinicalTrials.gov NCT06338904. Registered April 1, 2024.