Background: Several meta-analyses have examined the role of exercise interventions in improving psychological outcomes in cancer survivors but most did not focus on adjuvant therapy period and did not investigate the optimal dose of exercise needed. Methods: The present meta-analysis examines the impact of exercise interventions delivered at this particular period on fatigue, anxiety, depression and quality-of-life (QoL) as well as dose-response relationships between volume of prescribed exercise and these psychological outcomes. Randomized controlled trials that proposed an exercise intervention to breast cancer patients undergoing chemotherapy and/or radiotherapy were systematically identified and coded. Standardized mean differences (SMDs) of psychological outcomes were weighted by the inverse of their variances to obtain a pooled estimate using random effects model. Linear and quadratic regressions were carried out to explore dose-response relationships. Results: In total, 17 studies involving 1380 participants and 20 exercise interventions were included. Intervention subjects significantly reduced their fatigue and depression levels showing pooled effect sizes (EF) and their associated 95% confidence interval (95%CI) of -0.28 [95%CI: -0.54; -0.03] and -0.28 [95%CI: -0.46; -0.09] respectively. Levels of anxiety also appeared to be reduced but pooled estimate did not reach significance (p=0.06). Significantly increased QoL was observed: EF=0.34 [95%CI: 0.07; 0.62] favouring intervention. Consistent and significant inverse associations of weekly and total volume of prescribed exercise were observed with fatigue (F test: p=0.04, R²=0.19 and p=0.009, R²=0.26 respectively) and QoL (F test: p=0.01, R²=0.14 and p=0.02, R²=0.29 respectively), implying that SMDs magnitude decreased as exercise dose increased. Conclusions: Exercise intervention enhanced fatigue, depression and QoL in breast cancer patients undergoing adjuvant therapy. Prescription of relatively low doses of exercise (<12 MET.h per week) consisting in approximately 90-120 min of weekly moderate physical exercise seems more efficacious in improving fatigue and QoL than higher doses.