In a cluster randomized control trial, a school-based mental health program combining mental health literacy and dialectical behavior skills was implemented by teachers to determine effects on protective factors related to resilience for students in 3rd-12th grade. As part of a larger study, a subsample of 113 students with developmental disabilities attending 37 classrooms participated. Student-reported measures of self-concept, coping skills, and social support were collected three times in the year. Results indicated large effect sizes for the program on all measures, which pertain to time × group interactions (g = 1.53, 1.91, and 0.86 for self-concept, coping, and social support respectively). Follow-up analyses indicated that gains for the intervention schools primarily occurred between the first two assessment periods when the majority of program content was delivered. Implications for universal school-based mental health programming for students with developmental disabilities are discussed.