Aims: The purpose of the present study was to investigate healthy lifestyle changes during the period before and after breast cancer diagnosis in Taiwan. Materials and Method: Lifestyle changes during the period before and after cancer diagnosis were assessed by convenience sampling with a structured questionnaire for breast cancer survivors. Results: A total of 235 breast cancer survivors completed the healthy lifestyle scale. The mean values before and after breast cancer diagnosis of the participants were 3.27 and 3.73. The final five dimensions for the period before breast cancer diagnosis were: had not experienced stress; had exercised; had maintained sleep quality; had maintained body weight; and had maintained relationships. The final five dimensions for the period after breast cancer diagnosis were: sleep quality; had not experienced stress; relationship; had exercised; and had maintained body weight. A paired-t test was applied to examine the differences before and after cancer diagnosis, revealing that the total average scores of the participants on the healthy lifestyle scale clearly differed statistically (t= -17.20, p<0.01); and the nine dimensions before and after testing also demonstrate a marked statistical difference (p<0.01). Conclusions: These findings are helpful in understanding the healthy lifestyle changes during the period before and after cancer diagnosis among breast cancer survivors. It is expected that these results can offer references of self-care for this group of patients.