Background Free muscle flaps are a mainstay for reconstruction of distal third leg wounds and for large lower extremity wounds with exposed bone. However a major problem is the significant postoperative flap swelling, which may take months to resolve. We studied the efficacy and safety of immediate application of a vacuum assisted closure (VAC) dressing after a free muscle flap to the lower extremity. Methods Over a 19 months period, all consecutive free muscle flaps for lower extremity reconstruction at a Level I trauma center were evaluated prospectively for postoperative flap thickness, complications and flap survival. Immediate application of a VAC dressing was performed in 9 patients, while the flap was left exposed for monitoring in 8 patients. Results There was no statistically significant difference in flap survival between both cohorts. Mean flap thickness at postoperative day 5 for the VAC group was 6.4±6.4 mm, while flap thickness for the exposed flap group was 29.6±13.5 mm. Flap thickness was significantly decreased at postoperative day 5 for the VAC dressing group. Conclusions Immediate application of VAC dressing following free muscle flaps to the lower extremity does not compromise flap survival or outcomes and results in decreased flap thickness and a better aesthetic outcome.