Cognitive-behavioral treatments (CBTs) are widely used for anxiety disorders in typically developing children; however, there has been no previous attempt to administer CBT for specific phobia (in this case study, one-session treatment) to developmentally or intellectually disabled children. This case study integrates both cognitive-behavioral and behavior analytic assessment techniques in the CBT of water and height phobia in a 7-year-old male with developmental delays and severe behavior problems. One-session treatment [Ost, L. G. (1989). One-session treatment for specific phobias. "Behaviour Research and Therapy," 27, 1-7; Ost, L. G. (1997). Rapid treatment of specific phobias. In G. C. L. Davey (Ed.), "Phobias: A handbook of theory, research, and treatment" (pp. 227-247). New York: Wiley] was provided for water phobia and then 2 months later for height phobia. The massed exposure therapy sessions combined graduated in vivo exposure, participant modeling, cognitive challenges, reinforcement, and other techniques. Both indirect and direct observation measures were utilized to evaluate treatment efficacy. Results suggested CBT reduced or eliminated behavioral avoidance, specific phobia symptoms, and subjective fear. Negative vocalizations were reduced during height exposure following treatment. Vocalizations following treatment for water phobia were less clear and may have been indicative of typical 7-year-old protests during bath time. Findings indicate CBT can be effective for treating clinical fears in an individual with developmental disabilities and severe behavior. Future research in this population should examine CBT as an alternative to other techniques (e.g., forced exposure) for treating fears.