For decades, parental reports were used to assess children’s psychological symptoms and social problems. The Berkeley Puppet Interview (BPI) utilizes hand puppets to collect questionnaire-style interview data from children, allowing consideration of children’s own perspective. The current longitudinal study compared the feasibility and reliability of preschoolers’ self-report with BPI at age 4 (M = 4.03, SD = 0.16; 52% boy, 82% White American) and 5 (M = 5.22, SD = 0.36) as well as cross-informant agreement among children, mothers, alternate caregivers (> 90% biological fathers), and coders. Children completed Symptom, Prosocial, and Parenting scales of BPI and their parents completed surveys assessing similar constructs. Our findings revealed both similarities and changes across ages. Specifically, the reliability and cross-informant agreement of the broad Symptom and Parenting scales were promising at both timepoints; however, 4-year-olds showed lower internal consistency in Social scales. Recommendations for how to refine and utilize BPI appropriately in young children in future research and the importance of cross-informant design were discussed.