The purpose of this study was to examine how parental homework completion, session attendance, and treatment knowledge influenced parenting practices and confidence in using learned skills during behavioral parent training (BPT). Parents of 54 preschoolers (M[subscript age] = 5.07, 82% Hispanic/Latino) with externalizing behavior problems participated in an 8-week group BPT program. Pre-and posttreatment measures included parent-reported parenting practices and a treatment knowledge quiz. Parental homework completion, or home practice of skills, was reported by parents and collected weekly. Increases in positive parenting and decreases in negative parenting were observed (Cohen's "d" = 0.63 and 0.70, respectively), as well as increases in treatment knowledge ("d" = 1.46). Treatment knowledge moderated the association between parental homework completion and negative parenting as well as parenting skill-use confidence. Increased parental homework completion was only associated with decreases in negative parenting and increases in skill-use confidence for families with high treatment knowledge. Parental homework completion also moderated the association between session attendance and negative parenting, such that lower session attendance was only associated with higher negative parenting for families that had low parental homework completion. Findings highlighted the potential impact that parents' reports of home practice may have on improving parenting.