This study describes weight changes experienced by Malaysian women with breast cancer. Women withbreast cancer (n=368) were recruited from eight hospitals and four breast cancer support groups in PeninsularMalaysia. Current weight was measured and weight at the time of diagnosis and a year preceding diagnosiswere based on self-reports. Change in weight was determined from the year preceding breast cancer diagnosisto study entry (time 1), at the time of diagnosis to study entry (time 2) and from a year preceding breast cancerdiagnosis to the time of diagnosis (time 3). Current body mass index, at a year preceding diagnosis and at thetime of diagnosis were determined. Waist circumference was also measured. The sample comprised 57% Malay,34% Chinese and 9.8% Indian women. The mean age of the women was 54 ± 9.04 years and over 80% were postmenopausal.Majority of the women were in stage I and stage II breast cancer at the time of diagnosis. The mostcommon treatments received by these women were chemotherapy followed by radiotherapy and mastectomy.Overweight and obesity were prevalent in over 40% of the survivors at all three periods. Significant weightchanges were observed during time 1 (-0.74 ± 4.78kg, p< 0.001), time 2 (2.73 ± 8.06kg, p< 0.001) and time 3 (3.47± 7.53kg, p< 0.001). At time 1, almost 50% showed no changes in their weight. At time 2, nearly two-thirds hadgained weight and at time 3, 69% had gained weight, abdominal obesity was observed in nearly two-thirds ofthe women at study entry. A significant difference in weight change among age groups was observed in time 2and time 3. All ethnic groups had significant weight change in time 1 and time 2. Significant weight gain wasobserved in relation to body mass index prior to diagnosis, at diagnosis and at study entry. However, no significantdifference in weight change by educational level, family history of cancer and cancer stages were observed in all3 periods. In conclusion, significant weight gain was evident in this sample of women after diagnosis of breastcancer and treatment. Women with breast cancer should be encouraged to maintain normal body mass indexand waist circumference through appropriate diet and regular physical activity which may help to reduce theirrisk of recurrence, secondary cancer and metastasis.