Background <p>Patients with incisional hernia (IH) frequently present severe comorbidities and require complex preoperative strategies before incisional hernia repair (IHR). To date, no study has evaluated the relationship between preoperative physical activity level and the occurrence of serious complications after IHR. Therefore, the aim of this study was to investigate the influence of preoperative physical activity level on serious complication incidence.</p> Methods <p>A single-center prospective cohort pilot study was conducted, including all patients who underwent IHR between January 2021 and October 2024. The ACTI-MET^® tool was used to assess preoperative physical activity. Preoperative functional activity assessments included the Six-Minute Walking Test (6MWT), HandGrip Strength Test (HGST), and Timed Up and Go Tests (UGT). Postoperative complications were graded using the comprehensive complication index (CCI) and Dindo-Clavien (DC) classifications. A serious complication was defined as CCI ≥ 42.4%.</p> Results <p>A total of 127 patients were included. The distance covered by patients during the 6MWT was, on average, 225&#xa0;m shorter than the expected standard (6MWTev). There was a significant correlation between patients with postoperative serious complications and low preoperative physical activity as evaluated with the ACTI-MET^® tool. Only the UGT was correlated with preoperative physical activity, but standard functional tests such as 6MWT, UGT, and HGST failed to predict serious complications. The presence of a serious complication significantly increased the mean length of hospital stay by a 2.69 ratio (15 vs. 5.56 days; <i>p</i> &lt; 0.01).</p> Conclusion <p>Preoperative physical activity evaluated with the ACTI-MET^® tool could help to predict serious complication occurrence. Further studies are needed to explore the potential benefits of preoperative activity optimization programs and prehabilitation on hernia surgery outcomes.</p>