Background <p>Breast cancer is the leading cancer type among women, accounting for 24.5% of female cancer cases worldwide.</p> Objective <p>The purpose of this study is to systematically review and conduct a meta-analysis to evaluate the effects of exercise interventions on breast cancer patients at different stages of treatment.</p> Methods <p>Databases including PubMed, Cochrane Library, and Embase were searched for English-language randomized controlled trials (RCTs) published since 2000. The study included data from women aged 18 and above with breast cancer, either undergoing treatment or after treatment. Effect sizes were calculated using the standardized mean difference.</p> Results <p>Out of 2845 studies, 40 met the inclusion criteria, with 17 studies focusing on patients undergoing treatment and 23 on after treatment patients. Exercise significantly reduced fatigue both undergoing (<i>d</i> =  − 0.20) and after treatment (<i>d</i> =  − 1.11). After treatment exercise interventions resulted in improvements in lean mass (<i>d</i> = 1.27), fat mass (<i>d</i> =  − 1.33), percentage body fat (<i>d</i> =  − 1.22), and waist circumference (<i>d</i> =  − 0.69). Additionally, biomarkers such as IL-6, HDL, LDL, glucose, systolic blood pressure (SBP), and diastolic blood pressure (DBP) showed improvements after treatment.</p> Conclusions <p>Exercise interventions are effective in reducing fatigue and enhancing fitness while undergoing treatment and have positive effects on body composition and biomarkers after treatment. Low-to-moderate intensity exercise is recommended undergoing treatment, while moderate-to-high intensity exercise is beneficial after treatment.</p> <p>Implications for Cancer Survivors.</p> <p>Personalized exercise programs should be incorporated as a standard part of care in clinical settings to alleviate fatigue undergoing treatment and improve body composition and biomarkers following treatment.</p>