Objective: To analyze the factors affecting the occurrence of psychological imbalance in chemotherapy patients after modified radical surgery for breast cancer. Methods: Retrospectively analyzed the clinical data of 285 postchemotherapypatients with breast cancer who received chemotherapy treatment in a hospital between November 2022 and December 2023 and applied to analyze the incidence rate of psychological imbalance and influencing factors by using logistic regression analysis. Results: Psychological imbalance occurred in 178 cases of 285 post-chemotherapy patients after modified radical mastectomy for breast cancer, accounting for 62.46%. Comparing the patients in the occurrence group and the non-occurrence group in terms of age, family history, marital status, place of residence, and per capita monthly income of the family, the differences were not statistically significant (P > 0.05), whereas in terms of high school or lower education level, low social support, and having a burden of self-feeling, the proportion of the occurrence group was higher than that of the non-occurrence group, and the differences were statistically significant (P < 0.05). Conclusion: The risk of psychological imbalance is higher in patients undergoing chemotherapy after modified radical mastectomy for breast cancer, while high school and below educational background, low social support, and having self-perceived burdens are the main risk factors (OR > 1, P < 0.05).