BackgroundElevated body mass index (BMI) is a known perioperative risk factor for complications such as delayed wound healing and infection. However, there is a gap in understanding how elevated BMI impacts outcomes after posttraumatic lower extremity (LE) microvascular reconstruction.MethodsA retrospective review was performed at a level 1 trauma center between 2007 and 2022 of patients who underwent posttraumatic microvascular LE reconstruction. Demographics, flap/wound details, complications, and outcomes were recorded. Patients were stratified into BMI Center for Disease Control categories.ResultsA total of 398 patients were included with an average BMI of 28.2 ± 5.8. Nearly half (45%) of LE defects were located in the distal third of the leg, 27.5% in the middle third, and 34.4% in the proximal third. Most reconstructions utilized muscle‐containing flaps (74.4%) compared with fasciocutaneous flaps (16.8%). Surgical approaches included free flaps (47.6%) and local flaps (52.5%). Class III obese patients were significantly more likely to be nonambulatory than nonobese patients (OR: 4.10, 95% CI 1.10–15.2, p = 0.035). At final follow‐up, 30.1% of patients with Class III obesity were ambulatory, requiring either wheelchairs (42.3%) or assistance devices (26.9%). There were no significant differences in complication rates based on obesity status (0.704). The average follow‐up time for the entire cohort was 5.8 years.ConclusionsBMI is critical for patient care and surgical decision‐making in LE reconstruction. Further research is warranted to optimize outcomes for higher BMI patients, thereby potentially reducing the burden of postoperative complications and enhancing overall patient recovery.