Aim: Studies on obese individuals have proposed a correlation between weight loss and variations in mean platelet volume (MPV). Therefore, this study aimed to examine the changes in MPV in morbidly obese patients who underwent weight loss via bariatric surgery. Material and Methods: A total of 328 morbidly obese patients who underwent sleeve gastrectomy (morbidly obese group) and were retrospectively evaluated from January 2010 to November 2014. The control group consisted of 53 non-obese patients who had laparoscopic cholecystectomy. Body mass index values and MPV values at preoperative (baseline), postoperative 1st month, 3rd month, and 12th month for both groups were documented. Results: The baseline MPV values were comparable between morbidly obese group and control group (8.8 ± 1.8 vs. 8.6 ± 1.2, p = 0.283). In control group, there was no significant change in MPV levels during the 12-month follow-up. In morbidly obese group, mean MPV levels at the 1st and 3rd months post-surgery were similar, showing an increase compared to baseline levels. By the 12th month, mean MPV levels tended to decrease, becoming comparable to baseline values. Conclusion: MPV levels increased in the early postoperative period following sleeve gastrectomy, they returned to baseline by the 12th month. These findings suggest that weight loss from bariatric surgery may influence MPV levels, but this effect normalizes over time.