Purpose: Weight gain after diagnosis of breast cancer is a profound issue that may negatively impact cancer prognosis. However, most existing research on weight change has been conducted in Western countries. In addition, several factors related to weight gain have been reported; however, the evidence is inconsistent. The purpose of this study was to examine weight gain and its correlates among Korean breast cancer survivors. Methods: A total of 132 female breast cancer survivors were recruited from one university hospital in South Korea. Participants completed anthropometric measurements (i.e., body weight, height) and a self-reported questionnaire, including the International Physical Activity Questionnaire Short Form and Mini Dietary Assessment. Results: The mean weight change was -0.09 kg (SD = 4.28). Only 27 women (19.7%) gained more than 5% of their weight at diagnosis, 59.1% maintained weight, and 21.2% lost weight. In multivariate logistic regression analysis, significant correlates of weight gain were younger age, obesity at diagnosis, duration of more than 36 months since diagnosis, and low diet quality. Conclusion: Younger women, women who were obese at diagnosis, women with more than 36 months since diagnosis, or women who showed lower diet quality should be considered at high-risk for weight gain. Findings from our study suggest that optimal weight management strategies should be developed using ethnically- or culturally-appropriate approaches.