Background Surgical resection of the oral cavity squamous cell carcinoma with clear surgical margins is the key to preventing local recurrence and avoiding the need for adjuvant treatment or margin re-resection. There is often a discrepancy observed between the clinically determined margins of the tumor when it is being resected and the histopathological result after the specimen has been processed. Methods A total of six patients who underwent primary surgical resection of oral squamous cell carcinoma between June and October 2020 were included. Surgical margins of the tumor were measured and recorded at three stages of tumor resection: pre-incision, post-resection, and post-formalin fixation. The 1 cm pre-incision anterior margin was compared to both the anterior post-resection and post-formalin fixation margins to document any shrinkage between the different stages of tumor resection. Results The overall mean surgical margin shrinkage was 26% (95% confidence interval {CI} 9.34-42.66, p=0.012). The greatest amount of margin shrinkage occurred between pre-incision and post-resection measurements, which is statistically significant at 19.7% (95% CI 7.49-31.83, p=0.009). To a lesser extent, tumor surgical margins also decreased by 12.7% (95% CI -2.66 to 28.09, p=0.083) between post-resection and post-formalin fixation. Conclusion Dimensions of tumor surgical margins in oral cavity squamous cell carcinoma specimens decrease from surgical resection to histopathological processing. Most of this shrinkage occurs between the clinically determined pre-incision and immediately after tumor resection in the post-resection measurement. These findings suggest that it might be prudent to consider surgical margin shrinkage when outlining initial margins to ensure adequate and complete resection of the tumor.