We observed the relief of hot flashes in breast cancer survivors taking tamoxifen and treated with sertraline for depression. Our objective was to assess the effect of sertraline on the frequency and severity of hot flashes, mood status, and health-related quality of life. We used a randomized, double-blind, placebo-controlled, crossover study using 6 weeks of sertraline (50 mg each morning) versus placebo. Study participants were 62 breast cancer survivors from an oncology clinic in a tertiary care center on adjuvant tamoxifen reporting bothersome hot flashes. Patients were asked to keep a daily hot flash diary to record hot flash frequency and severity, from which hot flash scores (frequency x severity) were calculated. The Center for Epidemiologic Studies depression scale and Functional Assessment of Cancer Therapy--Breast (FACT-B) (at baseline, 6 weeks, and 12 weeks) were used to assess mood and quality of life. Sixty-two women were accrued. Forty-seven women (median age 53.9 years, range 36.6-77.1 years; 89% postmenopausal; 85.5% Caucasian) completed the first 6 weeks and 39 completed 12 weeks. The baseline daily hot flash frequency and score were 5.8 (standard deviation 4.1) and 11.5 (14.0), respectively. At the end of the first 6 weeks, hot flash frequency decreased by 50% in 36% of those taking sertraline compared to 27% taking placebo. In the crossover analysis, sertraline was significantly more effective than placebo: women crossing from placebo to sertraline had a decrease (-0.9 and -1.7) in hot flash frequency and score, whereas those crossing from sertraline to placebo had an increase (1.5 and 3.4) in hot flash frequency and score (p = 0.03 and 0.03). Forty-eight percent preferred the sertraline period, 11% preferred the placebo period, and 41% had no preference (p = 0.006). Measures of depression and quality of life were within normal range and did not change significantly within treatment groups. Sertraline decreases hot flashes in breast cancer survivors taking tamoxifen and women prefer sertraline to placebo. Further study of sertraline for the management of hot flashes is warranted.