Behavioral parent training (BPT) is an evidence-based intervention for the treatment of attention-deficit/hyperactivity disorder and related disruptive behavior disorders in youth. Although efficacious, dropout from BPT is a notable issue, particular for high-risk families. The literature suggests that parental factors (stress, psychopathology and cognitions) may be particularly important in understanding which parents dropout from BPT. To date, however, limited attention has been given to how these factors may be related to dropout at varying points during BPT. Secondary data analyses from a completed clinical trial of a traditional BPT intervention is presented herein. Forty participants were classified into three groups based on timing of dropout from BPT (enrolled in but never attended BPT; dropped out during BPT, and completed BPT). Parent-level factors (stress, depressive symptoms, parental efficacy, and parental attributions for child behavior) were assessed at baseline and post-treatment (parental perceived barriers to treatment) to determine if these factors were differentially related to dropout group status. Results suggested that parents who never attended BPT were more likely to have lower parental efficacy and greater maladaptive attributions regarding their child compared to parents who dropped out from BPT and those who completed BPT. Moreover, parents perceptions of the relevance of BPT was lower in the never attended group and the dropped out from BPT group compared to the completed BPT group. Results of the study have implications for tailoring engagement strategies focused on parental cognitions throughout the process of BPT, particularly for high-risk families.