Purpose: Tracking of infants' progression through early vocal stages supports the identification of children at risk for language delays and guides early intervention for children with disabilities. However, few clinical tools are available to support systematic assessment of infants' early vocal development. This study sought to develop and conduct a preliminary evaluation of the validity of a parent report tool designed for this purpose, the Vocal Development Landmarks Interview (VDLI). Method: The participants were caregivers of 160 typically developing 6- to 21-month-old infants. Caregivers participated in the VDLI, which uses audio samples of authentic infant vocalizations to query parents regarding their children's vocal behaviors. The VDLI yields 3 subscale scores (Precanonical, Canonical, and Word) and a total score. Caregivers also completed sections of the Communication and Symbolic Behavior Scales Developmental Profile Caregiver Questionnaire that yielded a speech composite score. Results: Cross-sectional analyses showed that the VDLI is sensitive to age and captures the expected developmental trajectories of vocal behaviors. A strong, positive correlation (r = 0.93) was found between VDLI total scores and the Communication and Symbolic Behavior Scales Developmental Profile speech composite score, indicating concurrent validity. Subscales were found to be internally consistent. Conclusion: Preliminary findings of sensitivity to age, concurrent validity, and internal consistency provide support for the eventual use of the VDLI as a clinical tool for tracking vocal and early verbal milestones. Future research will explore the level of concordance between parent report and researcher observations of child vocal behaviors.