Animal well-being and enrichment continue to gain importance in the maintenance of primates living in captivity. Positive reinforcement training (PRT) and/or playing interaction have been shown to be effective in improving the well-being of several species of primates. This research study evaluated the effects of applying a combination of these two techniques (training/playing therapy) on a group of lowland gorillas (Gorilla gorilla gorilla). The effects of this combination on the behaviour of captive primates have been given very little attention to date. The behaviour of a group of seven females was recorded in two different phases at Barcelona Zoo: before (periods 1 and 2) and after (periods 3 and 4) a series of changes were made to the composition of this social group. In each period, two phases were distinguished: i) baseline condition, after the subjects became used to the researcher, focal recordings were made of the group's regular behaviour and, ii) experimental condition, the training and playing sessions ('gorilla play') with two specific subjects began one hour before the group went to the outdoor facility. The frequency and duration of the behaviour observed in each of the recording conditions were compared. The results showed positive changes in the gorillas' behaviour: stereotypies, interactions with the public, aggression between subjects and inactivity were all reduced, while affiliative behaviour and individual and social play-related behaviour increased. Moreover, the benefits of this therapy were observed in trained individuals and the rest of the gorillas in the group, which would seem to indicate that training/playing can be used to create a more relaxed atmosphere, reducing social tension and improving the well-being of all the subjects involved.