In the current research the effectiveness of cognitive therapy based on Mindfulness has been investigated on the reduction of posttraumatic stress symptoms and increasing the Autobiographical memory and quality of life in treated patients with breast cancer. The current research is a quasi experimental research with pretest-post-test and control group in a 60-day follow up.24 treated women with breast cancer were selected among the age of 25 to 55 who went to radiation and oncology department of Chamran , Baghiyatallah , Besat and surgery department of Eram clinic and were placed in two experimental and control groups.12 healthy women were also selected (without any history of illness) that were made homogenous in variables of age , level of education , marital status and occupation. SCID interview , autobiographical memory test (AMT),quality of life questionnaire (QLQ) and revised impact of events scale were carried out .The experimental group had been under MBCT training for eight 2-2.5- hour- sessions. Results were analyzed by the use of 18th copy of SPSS software. Applying covariance analysis indicated that MBCT training courses are effective in the reduction of posttraumatic stress symptoms and increase in the quality of life .Also considering the results obtained in follow up ,it can be said that this method can be effective in reduction and prevention of PTSD from getting worse and increasing the Autobiographical memory in treated patients with breast cancer. applying MBCT in medical centers can be considered as a rehabilitation treatment after treating and can play an important role in solving many physical and mental problems that lessens the quality of life