Background: Severe primary mitral regurgitation (MR) poses a significant clinical challenge, and surgical correction is often necessary to improve outcomes. However, the ability to predict post-surgical results is still a critical concern. This research aimed to investigate the function of myocardial strain, specifically global longitudinal strain (GLS), in predicting outcomes after surgery for severe MR. Methods: This prospective cohort research was undertaken on 104 individuals with severe primary MR who had repair or replacement of the mitral valve. Transthoracic echocardiography and speckle-tracking analysis were conducted to assess myocardial strain. Results: Patients experiencing the primary endpoint (a composite of rehospitalization for heart failure, cardiac mortality, and redo surgery) demonstrated significantly lower baseline GLS (-14.1 ± 3.4 vs. -18.3 ± 2.5, P-value < 0.001) compared to those without the endpoint. ROC analysis exhibited that baseline GLS was an excellent predictor of the primary endpoint (AUC = 0.846, P-value < 0.001). Multivariate logistic regression confirmed that baseline GLS was a significant predictor of the primary endpoint (OR = 0.566, 95% CI = 0.445 – 0.719, P-value < 0.001). Kaplan-Meier analysis exhibited that patients with GLS ≤ 17.9 had significantly lower endpoint-free survival rates. Conclusion: GLS seems to be a more accurate predictor of cardiac events than all-cause mortality following surgery for severe MR. In patients with severe primary MR, measuring preoperative GLS is useful for predicting postoperative prognosis and deciding the appropriate schedule for surgery.