In vivo therapeutic coaching of parent-child interactions is the primary mechanism of change in behavioral parent training programs such as parent-child interaction therapy (PCIT), yet relatively little research has examined the coaching process. The primary aim of this study was to explore the bidirectional interaction between therapist-parent dyads to better understand how therapists influence parent behavior and vice versa. Observational data from two research projects were analyzed separately and together using lag sequential analysis (LSA). Results demonstrate that therapist responsive coaching (e.g., praising parent behavior) led parents to use more child-centered skills. Responsive coaching techniques led to immediate increases in parents’ use of the targeted positive parenting skill (10%–25% re-use). Responsive strategies followed targeted parent verbalizations more often than directive strategies, suggesting that therapists reinforce positive parenting skills as soon as parents use them. When directive coaching techniques were used, there was a 18% to 32% chance that parents followed through with a child-centered skill as coached. This study is the first to explore the influence of in vivo coaching on parent skill acquisition on a micro-level and has implications for the therapist training.