Background: This study aims to evaluate the impact of perioperative fluid administration, defined as fluid delivered intraoperatively and in the postanesthesia care unit, on postoperative outcomes. Methods: Medical records of 102 patients with oral cavity squamous cell carcinoma undergoing free flap reconstruction between January 2011 and December 2015 were reviewed. The primary endpoint was development of a postoperative complication according to the Clavien-Dindo classification. Perioperative factors recorded were Washington University Head and Neck Comorbidity Index, operating time, vasopressor use, blood loss, intraoperative fluid, and perioperative fluid. Results: Greater perioperative fluid administration was independently associated with surgical complications, flap complications, overall incidence of any complication, and increased length of stay. Greater intraoperative fluid administration was independently associated with higher rates of surgical complications. Intraoperative delivery of vasopressors was not associated with flap or surgical complications. Conclusion: Receiving less perioperative fluid was associated with fewer complications and decreased length of stay. K E Y W O R D S free tissue transfer, head and neck cancer, intraoperative fluid, oral cavity squamous cell carcinoma, perioperative fluid, postanesthesia care unit, postoperative complication