Very little is known about factors potentially affecting the performance of therapists delivering applied behavior analysis (ABA) interventions for young children with autism. Eighty-one therapists working in ABA schools participated in a questionnaire study focused on their reports of burnout and perceived therapeutic self-efficacy in their work role. Perceived supervisor support played a central role in the prediction of reduced therapist burnout and increased therapeutic self-efficacy. In addition, perceived supervisor support moderated the impact of work demands on personal accomplishment burnout. Those therapists reporting high work demands and lower levels of supervisor support had lower personal accomplishment scores on the Maslach burnout inventory. Clinical implications include the importance of supervisor support for therapists and also supervisor style.