The aim of this investigation was to evaluate how parental anxiety predicted change in pediatric anxiety symptoms across four different interventions: cognitive-behavioral therapy, medication (sertraline; SRT), their combination (COMB), and pill placebo. Participants were 488 youths (ages 7–17) with separation anxiety disorder, generalized anxiety disorder, and/or social phobia and their primary caregivers. Latent growth curve modeling assessed how pre-treatment parental trait anxiety symptoms predicted trajectories of youth anxiety symptom change across 12 weeks of treatment at four time points. Interactions between parental anxiety and treatment condition were tested. Parental anxiety was not associated with youth’s pre-treatment anxiety symptom severity. Controlling for parental trait anxiety, youth depressive symptoms, and youth age, youths who received COMB benefitted most. Counter to expectations, parental anxiety influenced youth anxiety symptom trajectory only within the SRT condition, whereas parental anxiety was not significantly associated with youth anxiety trajectories in the other treatment conditions. Specifically, within the SRT condition, higher levels of parental anxiety predicted a faster and greater reduction in youth anxiety over the acute treatment period compared to youths in the SRT condition whose parents had lower anxiety levels. While all active treatments produced favorable outcomes, results provide insight regarding the treatment-specific influence of parental anxiety on the time course of symptom change.