We evaluated the effects of tact training when instruction was presented in English only compared to tact training in a bilingual format (in English and the home language, Portuguese) for a participant diagnosed with a communication disorder. The participant's parents completed a questionnaire describing his exposure to both languages prior to the start of the study. We also conducted formal language assessments to determine the participant's preexisting language abilities. An adapted alternating treatment design was used to compare the rate of acquisition in the two training conditions. Results show the participant emitted more correct responses during tact training in English than during the bilingual tact training. Generalization and maintenance of acquired tact responses for stimuli trained in the bilingual condition were greater than for stimuli trained in the English-only condition. These results are discussed with respect to implications for language-training programs for children with language delays and developmental disabilities, and we outline suggestions for future research in this area.