Objective This study is a pragmatic randomized controlled trial, which compares the effectiveness of an adapted form of Dialectical Behavior Therapy for Adolescents (DBT-A) and treatment as usual plus group sessions (TAU + GS) to reduce suicidal risk for adolescents in a community health mental clinic. Method Thirty-five adolescents from a community outpatient clinic, with repetitive NSSI alone or with SA over the last 12 months and with current high suicide risk as assessed by the Columbia-Suicide Severity Rating Scale (C-SSRS), were enrolled. Participants were randomly assigned to undergo either DBT-A (n = 18) or TAU + GT (n = 17) treatments over a 16-week period. Primary outcomes were the difference between NSSI and SA recorded during the first 4 weeks and the final 4 weeks of treatment. Secondary outcomes included changes in Children’s Global Assessment Scale (C-GAS), Suicidal Ideation Questionnaire (SIQ-JR), and Beck Depression Inventory-II (BDI-II). Results Dialectical Behavior Therapy for Adolescents was more effective than TAU + GS at reducing NSSI, use of antipsychotics, and improving C-GAS. No SAs were reported in the two groups at the end of the treatment. Both treatments were equally effective in decreasing SIQ-JR and BDI-II scores. Conclusions These findings support the feasibility and effectiveness of DBT-A for adolescents at high risk of suicide in community settings.