Background: The width of the surgical resection margin impacts recurrence and survival in oral cavity squamous cell carcinoma (OSCC). The most commonly used definition of a clear margin is one larger than 5 mm, although due to anatomical restrictions to e.g. bone or vessels, this size is not always feasible. Margins less than 5 mm affect postsurgical strategies and prognoses, and further knowledge of margins smaller than 5 mm is needed.Aims/objectives: We aimed to systematically review the literature on the impact of surgical resection margins less than 5 mm addressing recurrence and survival in OSCC.Methods/materials: A systematic literature search was performed in the PubMed and EMBASE databases identifying studies regardless of publication date that examined margin less than 5 mm, with or without a comparison to size of 5 mm or greater, in patients with OSCC. We assessed the impact on recurrence and survival.Results: We identified six studies (n = 1514 patients); all studies, investigated recurrence, and three (n = 768 patients) evaluated survival. The studies had noteworthy variability in, e.g. follow-up times, anatomical sublocations, T- and N-stage classifications, and outcome measures. Five studies (n = 1387 patients) reported that margins smaller than 5 mm would be safe and would not affect survival or recurrence negatively compared to their own data on larger margins. One study reported that a clear resection margin greater than five mm was necessary to ensure optimal outcomes.Conclusion/significance: The literature showed significant bias and risk issues. In five of the included studies with 1387 patients, we found in selected cases, where margins larger than 5 mm are not possible, a tendency regarding resection margins less than 5 mm to be sufficient for the surgical treatment of patients with primary OSCC. However, the data is insufficient to enable altered recommendations of resection margins in patients with primary OSCC.