Problem: A significant concept in psychodynamic theory and practice is that of defence mechanisms. The identifications of defences is a key task of the therapist and these are then used in the formulation and form part of the therapist's interventions. Case studies of psychotherapy with adults who have intellectual disabilities (IDs) suggest that they use more primitive defences but this has not been empirically evaluated. This study aimed to find out what defences adults with IDs use within and across sessions of individual psychotherapy. Methods: Transcripts of psychotherapy sessions with a case series of eight adults with IDs were evaluated using the defence mechanism rating scale. Results: Contrary to expectation the participants were observed to use a wide range of defences from primitive to mature. There was evidence to suggest that participants had developed a defensive style, but little evidence to show change in defensive structure across the first eight sessions of treatment. Conclusions: This exploratory study shows that adults who have IDs use a range of defences in psychotherapy and have particular defensive styles. The results suggest that future studies may need more participants and a longer time frame to see if change in defences occurs during psychotherapy. The defence mechanism rating scale may also need some validation work with adults who have IDs and consider inclusion of some defences that are disability-specific.