Expressive language is an important skill to develop in children with intellectual disabilities. It not only aids in decreasing the likelihood of challenging behaviors from occurring but also aids in increasing the individuals independence and assistance in them becoming successful members of society. No previous studies have examined the effectiveness of augmentative and alternative communication (AAC) interventions at increasing expressive language measured with mean length of utterances (MLU) in children with intellectual disabilities. The present study used an alternating treatment comparison design to evaluate the effectiveness of three communication interventions: (a) verbal imitation prompting, (b) American Sign Language prompting, and (c) simultaneous verbal imitation prompting and key word sign prompting on MLU in a 9-year-old child with intellectual disability. The study was conducted in the child’s classroom, and her teacher implemented the interventions. Results indicated simultaneous verbal and key word sign prompting were associated with the greatest MLU, although all three communication interventions appeared to increase MLU when compared with unprompted MLU. Implications for practice and future research in the area of simultaneous communication are discussed.