Background: The aims of the study were 1) to evaluate the incidence and types of postoperative complications after ablative oral cancer surgery with primary free flap reconstruction and 2) identify prognostic variables for postoperative complications. Material and Methods: Desired data was retrieved from a computer database at the department of Oral and Maxillofacial Department, Queen Elisabeth hospital Birmingham, United Kingdom, between June 2007 and October 2012. Logistic regression was used to study relationships between preoperative variables and postoperative outcomes. Results: The study population consisted 184 patients, comprising 189 composite resections with reconstruction. Complications developed in 40.2% of the patients. Three patients (1.6%) died, 11.1% returned to the operating room, 5.3% developed donor site complications and 6.9% flap complications of which 3.2% total flap failure. In the multivariable analysis systemic complications were associated with anaesthesia time and hospital stay with red cell transfusion. Conclusions: A significant proportion of the patients with primary free flap reconstructions after oral cancer surgery develops postoperative complications. Prolonged anaesthesia time and red cell transfusion are possible predictors for systemic complications and hospital stay respectively. Preoperative screening for risk factors is advocated for patient selection and to have realistic information and expectations.