For lung squamous cell carcinomas, there are no histologic findings that have been universally accepted as prognostic factors. Tumor budding and nuclear grade have been recognized as prognostic factors in other carcinomas. In this study, we investigated whether pathologic findings could determine clinical outcome in Japanese patients with lung squamous cell carcinomas. Tumor slides from surgically resected lung squamous cell carcinomas (1999 to 2012) were reviewed (n=216). Tumors were evaluated for histologic subtypes, differentiation, tumor budding, nuclear diameter, and mitosis. Recurrence-free survival (RFS) and overall survival (OS) were analyzed using the log-rank test and the Cox proportional hazards model. Tumor budding and large nuclei were independent prognostic factors of a worse RFS (P<0.001 and P=0.002, respectively) and a worse OS (P<0.001 and P=0.038, respectively) on multivariate analysis after adjustment for pathologic stage and lymphatic invasion. However, histologic subtypes, differentiation, and mitotic count did not correlate with prognosis. A grading system combining tumor budding and nuclear diameter was an independent prognostic factors of a worse RFS (grade 2 vs. 1, hazard ratio [HR]=2.91; P<0.001, and grade 3 vs. 1, HR=7.60, P<0.001) and a worse OS (grade 2 vs. 1, HR=2.15; P=0.014, and grade 3 vs. 1, HR=4.54, P<0.001). We found that a grading system combining tumor budding and nuclear diameter was a significant prognostic factor among Japanese patients with resected lung squamous cell carcinoma.