Problem behaviours in dogs rehomed through animal shelters can jeopardise the long-term success of adoptions. In this study, data from 61 adolescent and adult dog adoptions that occurred through an animal shelter in Auckland, New Zealand, from 1 November 2015 to 31 July 2016 were analysed to describe the frequency of problem behaviours and level of adopter concern at different time points post-adoption. Amongst the 57 dogs with behavioural information available, 40 (70%) had at least one reported problem behaviour, and the most frequently reported problem behaviours were poor manners (46%), destruction of household items (30%), and excessively high energy (28%). Very few dogs showed territorial aggression when objects or food items were removed (2% and 4%, respectively). However, aggression toward people or other dogs was frequently reported (19% and 19%, respectively). Of the 54 adopters that provided a response about their level of concern over their dog’s problem behaviours, 24 (44%) were not concerned at all, 23 (43%) were a little concerned, 4 (7%) were moderately concerned, and 3 (6%) were very concerned. Based on our interpretation of these findings, post-adoption support programmes targeted toward teaching adopters how to correctly train their dogs may be beneficial to increasing adoption satisfaction.