Background: This study aims to evaluate the strength of the association between frailty and intraoperative/postoperative complications in patients undergoing minimally invasive surgery (MIS) for endometrial cancer. Methods: In this retrospective observational multicenter cohort study, frailty was defined beforehand by a modified frailty index (mFI) score of ≥3. Multiple logistic regressions were performed to investigate possible preoperative predictors—including frailty, age, and body mass index—of intraoperative and early (within 30 days from surgery) or delayed (beyond 30 days from surgery) postoperative complications. Results: The study involved 577 women, of whom 6.9% (n = 40) were frail with an mFI ≥ 3, while 93.1% (n = 537) were non-frail with an mFI of 0–2. Frail women had a significantly higher rate of intraoperative complications (7.5% vs. 1.7%, p = 0.01), with odds 4.54 times greater (95% CI: 1.18–17.60, p = 0.028). There were no differences in the rate of early postoperative complications (15% vs. 6.9%, p = 0.06) and delayed postoperative complications (2.5% vs. 3.9%, p = 0.65) for frail versus non-frail patients. The odds of early postoperative complications increased by 0.7% (95% CI: 1.00–1.15) for every one-unit increase in age (p = 0.032). Conclusions: Frailty was associated with a significantly higher risk of intraoperative complications in older women undergoing MIS for endometrial cancer. Likewise, increasing age was an independent predictor of early postoperative complications. Our findings support the practice of assessing frailty before surgery to optimize perioperative management in this patient population.