Purpose: To investigate a model of language development for nonverbal preschool-age children learning to communicate with augmentative or alternative communication. Method: Ninety-three preschool children with intellectual disabilities were assessed at Time 1, and 82 of these children were assessed 1 year later, at Time 2. The outcome variable was the number of different words the children produced (with speech, sign, or speech-generating devices). Children's intrinsic predictor for language was modeled as a latent variable consisting of cognitive development, comprehension, play, and nonverbal communication complexity. Adult input at school and home, and amount of augmentative or alternative communication instruction, were proposed mediators of vocabulary acquisition. Results: A confirmatory factor analysis revealed that measures converged as a coherent construct, and a structural equation model indicated that the intrinsic child predictor construct predicted different words children produced. The amount of input received at home, but not at school, was a significant mediator. Conclusions: The hypothesized model accurately reflects a latent construct of Intrinsic Symbolic Factor (ISF). Children who evidenced higher initial levels of ISF and more adult input at home produced more words 1 year later. The findings support the need to assess multiple child variables and suggest interventions directed to the indicators of ISF and input.