The Use of Complementary and alternative medicine (CAM) is a common phenomenon among women with breast cancer in Malaysia. This study examines the prevalence, types, influencing factors and source of information regarding CAM among women with breast cancer, using a cross sectional research design. A purposive sampling was used to recruit 103 women with breast cancer who were attending follow up care at the Radiotherapy and Oncology unit of Universiti Kebangsaan Malaysia Medical Centre. Data was gathered through the use of self–administered questionnaires. Ninety one women identified themselves as CAM users while twelve were non users. Among the CAM users, 57(62.6%) were Malays, 27(29.7%) Chinese and 7(7.7%) Indians. The common types of CAM used were vitamins, nutritional supplements and traditional medicines (TM). CAM was used more frequently upon diagnosis (63.7%) and after completion of conventional treatment (97.8%). With regard to decision-making, most of the women (62.6%) did not make the decision to use CAM and were mostly influenced by their husband and mother (67%). Mother (71.4%), husband (67%), and relatives (56%) were the main sources of information and all values showed significant association with CAM use (p<0.05). Prevalence of CAM use, especially TM, was high among the Malay and Chinese ethnic groups. The lack of autonomy in decision-making by the women was the major reason for the use of CAM. The effectiveness and safety of using TM upon diagnosis and in combination with conventional cancer treatment are of concern to the breast surgeons, oncologist and the health care team.