Background: In the prospective POWER-remote trial, 51% and 12% of overweight/obese breast cancer survivors randomized to either a remotely delivered behavioral intervention or self-directed approach, respectively, lost ≥5% of baseline weight. We collected patient-reported outcomes (PROs) to examine the impact of >5% weight loss on symptoms, physical function (PF), and wellbeing. We hypothesized a priori that, regardless of study arm, those with ≥5% weight loss would have improved PF at 6 months v. those who did not. Methods: Women with stage 0-III breast cancer, who completed local therapy and chemotherapy, with a BMI ≥25 kg/m² were randomized to the 12-month intervention or self-directed weight loss. POWER-remote consists of telephone coaching and online tracking of diet, activity and weight. Women in the self-directed arm received a lifestyle booklet. All women completed PROs at baseline, 6 and 12 months: PROMIS PF, pain, fatigue, anxiety, depression, sleep; FACT-endocrine symptoms; MOS-sexual function. PROs were summarized descriptively and changes within and between groups were tested with multivariable mixed effects models, adjusted for age and baseline weight. Results: From 2013-2015, 96 women enrolled; 83 were evaluable at 6 months. At 6 months, PF scores improved in those with ≥5% weight loss v. not. While endocrine symptoms, fatigue, and anxiety improved in the group who lost ≥5%, differences between groups were not statistically significant. There was no significant change in sexual function, depression, or sleep within or between groups. Similar findings were seen across domains at 12 months, except pain improved in the group losing ≥5%. Conclusions: For overweight/obese breast cancer survivors, PF and other PROs improved among patients who lost ≥5%. These results support the patient-centered benefits of weight loss in this population. Clinical trial information: NCT01871116.