This paper describes a preliminary investigation on the effectiveness of Dynamic Interpersonal Therapy (DIT). The research was undertaken in an inner London primary care psychological therapies service. Outcome data on the symptoms of depression [Patient Health Questionnaire-9 (PHQ-9)] and anxiety [Generalised Anxiety Disorder-7 (GAD-7)] were collected from service-users (n = 24) at the first and last episodes of treatment. There were statistically significant reductions in depression (PHQ-9) and anxiety (GAD-7) associated with DIT, with medium and large effect sizes, respectively. Overall, 75% of patients showed an improvement on the PHQ-9 and GAD-7 following DIT. When this was calculated as statistically reliable change, the improvements reduced to 42% for anxiety and 25% for depression. As this study was uncontrolled, the significance cannot be reliably attributed to DIT. Future research may aim to investigate DIT's effectiveness in different settings with a larger sample size, using appropriate comparison groups under controlled conditions.