NHS staff are expected to implement National Institute for Health and Care Excellence (NICE) recommendations in clinical settings, but in practice delivering effective treatment can be difficult. The aim of this article is to evaluate the effectiveness of a mindfulness-based cognitive therapy group in clinical practice with a heterogeneous inner London population. The data are presented from 28 people who attended an eight-week group programme. The reliable change index was used to calculate how many people improved, did not change or deteriorated, on measures of depression (PHQ-9), anxiety (GAD-7) and social functioning (WSAS). Outcomes are taken from three time points: assessment, post-treatment and three-month follow up. A comparison of subjects was also undertaken to examine differences between time points. Most participants’ scores on the PHQ-9 (n=19) and WSAS (n=20) were maintained. The effectiveness of mindfulness-based cognitive therapy groups in clinical practice corresponds with the evidence base – participants maintained or improved clinical and social functioning. Further research is needed to help determine effectiveness over a longer follow-up period.