Teacher stress is a serious and endemic concern. Mindfulness-based interventions show promise in reducing stress and increasing well-being by cultivating mindfulness and self-compassion. This feasibility trial evaluated a mindfulness-based programme customised for teachers. A sample of 89 secondary school teachers and staff were recruited and self-selected into the intervention (n = 49) or comparison (n = 40) conditions. Participants were asked to complete self-reports which measured stress (PSS), well-being (WEMWBS), mindfulness (FFMQ), and self-compassion (SCS; Kindness and Self-Judgement) at baseline and after the completion of the intervention. Results revealed that individuals in the intervention condition reported significant reductions in stress, and significant increases in well-being post-intervention in comparison to their counterparts in the comparison group. There was an observed large effect (ηp2 >.14) for the intervention on all outcome measures, an effect that was maintained when controlling for baseline differences between the intervention and comparison groups. Furthermore, the majority (95 %) of teachers who attended the course found it to be acceptable. These results indicate that a customised mindfulness-based programme for teachers is a promising approach to reducing stress and increasing well-being, mindfulness, and self-compassion among secondary school teachers. However, the results of the current study are preliminary and the next phase of work will involve extending to a larger scale randomised controlled trial.