Cognitive Behaviour Stress Management for women with breast cancer has demonstrable empirical efficacy, however its effectiveness in the applied clinical setting has not been examined to date in an Australian setting. A 10-week group program was offered to five women with early stage breast cancer. Clinical changes in distress, coping, and social support from pre-test, to post-test and 1-month follow-up are reported. Overall, the group yielded strong favourable effect sizes indicating clinical improvement over time in PTSD symptoms and social support, but strong unfavourable effect sizes in cognitive avoidance. In terms of clinical cut-offs, all women met criteria for PTSD at baseline, with two women recovering at follow-up. The two participants with highest baseline distress experienced large improvements in depression, anxiety and PTSD at post-treatment, but rebounded to baseline at follow-up. Women qualitatively reported the major benefits of the program to be acquiring skills in relaxation and cognitive restructuring, and obtaining social support. This case study provides preliminary support that a CBSM program can improve PTSD and social support, however it raises concerns regarding the deteriorations observed in cognitive avoidance. Ways of addressing cognitive avoidance and the maintenance of gains warrants further investigation. (Contains 2 tables and 3 figures.)