While mentalising theory has become more widely known and utilized in recent years, there is not yet adequate integration of the theory and practice in the treatment of individuals who have developmental trauma and subsequently suffer from complex PTSD or dissociative disorders. This paper attempts to bridge that gap. The losses, inhibitions, or weakening of mentalising capacities in trauma are explained, along with how mentalising can be misused for personal gain in some situations, particularly to control and harm children who are abused. The relationship between neuroception – the neural detection of safety, danger or life threat – and mentalising is discussed, as well as how various motivational systems impact mentalising capacity. Therapists must be aware of clients’ loss of mentalising functions and the necessary interventions that are likely to restore these capacities, as well as their own inevitable lapses in mentalising that can serve as experiences that lead to relational repair and safety.