Autistic youth are at risk for internalizing mental health problems such as depression and anxiety. Similarly, parents of autistic youth report higher levels of depression than parents of typically developing children. The goal of this study was to examine bidirectional associations between parent depression symptoms and the internalizing problems of autistic youth in 188 families across four time points (T1–T4; spaced 12 months apart). A cross-lagged panel model revealed that mother (T1 and T2) and father (T1) depression symptoms positively predicted the youth’s internalizing problems 12 months later. The youth’s internalizing problems at T3 positively predicted maternal depression symptoms at T4. Future research should explore genetic and environmental pathways that link parent depression and internalizing problems in autistic youth.