Purpose: Parent report was compared to judgments made by a trained researcher to determine the utility of the Vocal Development Landmarks Interview (VDLI) for monitoring development of vocal behaviors in very young children. Method: Parents of 40 typically developing children, ages 6-21 months, provided full-day naturalistic audio recordings of their children's vocalizations after completing the VDLI. Six 5-min segments of highly voluble periods were selected from each recording and were analyzed, coded, and scored by the researcher. These data were then compared to the parents' VDLI responses. Parent--researcher agreement was examined using two methods and a generalized linear mixed model. Patterns of disagreement were explored descriptively to gain insights regarding potential sources of parent--researcher differences. Finally, developmental patterns in the researcher-observed vocal behaviors were examined as a function of children's age. Results: No significant differences in parent--researcher agreement were found for the Canonical and Word subscales of the VDLI; however, significant differences in agreement were found for the Precanonical subscale. Mean percentages of agreement were high overall for both scoring methods evaluated. Additionally, the researcher's categorization and quantification of vocal behaviors for each age group aligned well with developmental trajectories found in the literature. Conclusion: Results provide further support for use of parent report to assess early vocal development and use of the VDLI as a clinical measure of vocal development in infants and toddlers ages 6-21 months.