Background: This study examined reasons parents endorsed/provided for not completing homework tasks during their participation in a group-based behavioural parent training (BPT) intervention. Method: Eighty single mothers anonymously completed a questionnaire at the end of each of eight BPT sessions to ascertain reasons for not completing assigned homework. Results: Data suggests that there are varied reasons for poor HW completion that are related to various aspects of the homework process, but most notably the implementation phase of homework. Conclusions: Therapists should utilise various strategies to support homework completion, with special attention focused on methods for ‘in-vivo’ support for parents.