Objectives: Information on the prediction of improved semen parameters following varicocelectomy is scarce and mostly contradictory. Therefore, we developed and validated a nomogram to predict whether abnormal semen parameters in infertile men could improve following microscopic varicocelectomy (MSV). Methods: From January 2018 to December 2021, 460 consecutive patients who underwent MSV were included. Of them, 336 patients as a development cohort at the Xiang Hua institution. As a validation cohort, Hu Nan Center (124 patients) was used. Clinicopathologic patient information was recorded. The likelihood ratio test using Akaike’s information criteria was employed as the stopping rule, and multivariate logistic regression was utilized to create a prediction model with regression coefficients. The effectiveness of this prediction model was evaluated based on its ability of discrimination, calibration, and clinical utility. Results: The initial total progressively motile sperm count (TPMSC) and vein diameter were predictors of this model. The model demonstrated strong discrimination for the validation cohort, with an area under the receiver operating characteristic (AUROC) of 0.925 (p < 0.001), and strong calibration (unreliability test, p = 0.522). The decision curve study proved the model’s clinical applicability. Conclusion: According to our research, the improvement of semen parameters in infertile men following MSV was significantly predicted by greater vein diameter and higher initial TPMSC. This nomogram aids in individualized decision-making on the varicocele preoperative treatment plan and may help to enhance the therapeutic result.