Background: Behavioral parent training has been demonstrated to be an effective treatment for child behavior problems; however, lack of parent engagement can limit the effectiveness of treatment. Understanding more about predictors and correlates of a specific measure of parent engagement--homework completion--in parent training can help to improve treatment effectiveness and treatment outcomes. Objective: We examined predictors of homework completion, as well as the relationship between homework completion, treatment correlates, and treatment outcomes in an open trial of parent-child interaction therapy (PCIT), a behavioral parent training program. Methods: Participants included 53 families (mean child age = 4.40 years, SD = 1.43) who received PCIT in a community mental health center serving demographically (i.e., SES, ethnicity) diverse families. Results: Homework completion varied significantly between mothers and fathers but did not vary with other demographic family characteristics. Parents who completed treatment showed a somewhat greater likelihood of completing homework throughout treatment and a significantly greater likelihood of completing homework during the first phase of treatment. Additionally, parents who completed more homework were more likely to report higher levels of treatment satisfaction and showed a trend toward completing treatment in fewer sessions. Conclusions: Our findings suggest that homework has some benefits for treatment outcomes. Despite the benefits of homework, rates of adherence to homework were variable and below optimal levels. Study findings have implications for further understanding the role of homework in behavioral parent training programs.