There is limited research on job-embedded professional development designed to promote paraprofessionals' use of research-based strategies to support students with disruptive behaviors. This study serves as the first clustered randomized controlled trial to investigate the efficacy of the Behavior Support Coaching for Paraprofessional Model (BSC-P), which is a job-embedded training intervention for elementary schools. BSC-P is a data-driven coaching model designed to enhance paraprofessionals' implementation of behavior interventions for elementary school students with or at risk for disruptive behavior disorders. Within the present study, primary dependent measures included paraprofessionals' behavioral strategy implementation and perceived supports, the paraprofessional-teacher relationship, and work-related stress, as well as observed and rated student behaviors, academic engagement, academic achievement, and social skills. The sample included 259 students, 101 paraprofessionals, and 36 elementary schools randomly assigned to the BSC-P coaching condition or the waitlist control condition. Multilevel models revealed that, relative to those in the waitlist control condition, BSC-P paraprofessionals demonstrated improvements in behavior management practices (antecedent strategies d = 0.91, reward appropriate behavior d = 1.51) and emotional and instrumental support (ds = 0.60 and 0.63, respectively). No between-condition effects were found for perceived teacher paraprofessional relationships or work-related stress. Relative to students in the waitlist control condition, students supported by BSC-P paraprofessionals exhibited improvements in observed verbal and physical aggression (ds = -0.68) and academic engagement (d = 0.87), as well as teacher-rated school problems (d = -0.43), adaptive skills (d = 0.44), and social skills (d = 0.42). Paraprofessionals reported that BSC-P was an acceptable and useful professional development model.