Background/Objectives: Hartmann’s procedure is commonly employed to manage complications of acute sigmoid diverticulitis, such as perforation or abscess formation. However, determining the optimal timing for colostomy reversal remains a topic of debate. This study aims to evaluate the effect of early versus delayed colostomy reversal on postoperative outcomes, focusing on complications, hospital stay duration, and readmission rates. Methods: A retrospective cohort study was conducted on 148 patients who underwent Hartmann’s procedure for acute sigmoid diverticulitis at a single tertiary care center between 2014 and 2023. Participants were grouped based on the timing of colostomy reversal: early (45–120 days), intermediate (121–180 days), and late (>180 days). Data on complications, hospital stay length, and readmissions were analyzed. Results: Early reversal was associated with fewer postoperative complications, shorter hospital stays, and reduced readmissions compared to delayed reversal. The late reversal group had higher rates of complications, longer hospital stays, and a higher need for reintervention. Advanced age and comorbidities, such as cardiovascular disease and diabetes, were significant predictors of poor outcomes, contributing to delayed reversal. Logistic regression analysis indicated that late reversal was independently associated with higher complication rates. Conclusions: Early colostomy reversal within 45–120 days following Hartmann’s procedure is associated with improved postoperative outcomes, including fewer complications and a shorter hospital stay. The timing of colostomy reversal should be individualized based on patient health status, with early reversal preferred for those without significant comorbidities. Further prospective research is needed to confirm these findings and refine guidelines for optimal reversal timing.