To systematically review the literature to determine the prevalence of free flap failure in head and neck free flaps requiring vein grafting. Search strategies created in collaboration with a medical librarian were implemented using PubMed, Cochrane, Scopus, Web of Science, and Google Scholar from inception to August 2022. The population of interest included adult and pediatric patients undergoing reconstruction of oncologic or traumatic head and neck defects with a free flap requiring a vein graft that presents the success/failure rate. The primary outcome was the flap failure rate, and the secondary outcome was the flap compromise/revision rate. Inclusion and exclusion criteria were designed to capture all study designs. Initially, 2778 articles were identified by the search strategy. Two reviewers independently performed the review, data extraction for analysis, and a quality assessment. Primary Reporting Items for Systematic Reviews and Meta-analyses guidelines were followed. Meta-analysis was performed using a random effects model. Eleven studies of 789 flaps were included for data extraction. Random effects meta-analysis resulted in an estimated prevalence of free flap failure of 12.30% (95% confidence interval: 6.39%-19.49%, I2 = 77.4%). Taking into account that head and neck free tissue transfers that require a vein graft are typically associated with more challenging reconstructions and the lack of a suitable alternative, vein grafts appear to be a reliable method for bridging the gap between the flap and recipient vessels in head and neck free tissue transfer when indicated.