To identify valid measures of vocal development in young children with autism spectrum disorder in the early stages of language learning, we evaluated the convergent validity, divergent validity, and sensitivity to change (across 12 months) of two measures of vocal communication and two measures of vocal complexity through conventional coding of communication samples. Participants included 87 children with autism spectrum disorder (M = 23.42 months at entry). All four vocal variables demonstrated consistent evidence of convergent validity, divergent validity, and sensitivity to change with large effect sizes for convergent validity and sensitivity to change. The results highlight the value of measuring vocal communication and vocal complexity in future studies.