PURPOSE: Group-based mindfulness training is frequently described in psycho-oncology literature, but little is known of the effectiveness of mindfulness-based cognitive therapy (MBCT). We investigated the effectiveness and acceptability of MBCT for women with breast and gynecologic cancer. METHODS: Fifty women were recruited to participate in eight weekly 2-h mindfulness sessions. Outcomes of distress, quality of life (QOL), post-traumatic growth, and mindfulness were assessed pre-intervention, post-intervention, and again 3 months later using validated measures. Data were analyzed with repeated measures ANOVAs with a Bonferroni correction. Participant satisfaction and evaluation were also assessed. RESULTS: Forty-two women completed the program, and complete data were available for 36 women. Significant improvements with large effect sizes (ηρ(2)) were observed for distress (P < 0.001; ηρ(2) = 0.238), QOL (P = 0.001; ηρ(2) = 0.204), mindfulness (P < 0.001; ηρ(2) = 0.363) and post-traumatic growth (P < 0.001; ηρ(2) = 0.243). Gains were maintained 3 months post-intervention. Improvements in outcomes did not differ based on diagnostic group, psychological status, or physical well-being at entry. Change indices further support these findings. Scores on measures of distress, QOL, and post-traumatic growth decreased as a function of increased mindfulness at each time point (all P < 0.05). Participants reported experiencing the program as beneficial, particularly its group-based nature, and provided positive feedback of the therapy as a whole as well as its individual components. CONCLUSIONS: Within the limits of a non-randomized trial, these findings provide preliminary support for the potential psychosocial benefits of MBCT in a heterogeneous group of women with cancer. Future, more comprehensive trials are needed to provide systematic evidence of this therapy in oncology settings.