Glomeruloid microvascular proliferation (GMP) is a focal proliferative budding of endothelial cells (ECs) resembling a renal glomerulus. Whereas some experimental and clinical studies have suggested recently that GMPs indicate an aggressive angiogenic phenotype, the incidence and clinical significance of GMPs remains unclear. Thus, we conducted a retrospective study on GMPs in a total of 236 patients with completely resected pathological (p-) stage I-IIIA NSCLC. ECs were highlighted with immunohistochemical staining using an anti-CD34 antibody, and GMPs were defined as focal glomerulus-like aggregates of closely associated and multilayer CD34-positive ECs. Expression of vascular endothelial growth factor, angiopoietin (Ang)-1, and Ang-2 was also examined immunohistochemically. GMPs were positive in 60 (25.4%) patients, and the incidence was not correlated with age, gender, histological type, or p-stage. The mean intratumoral microvessel densities for GMP-negative tumor and GMP-positive tumor were 178.2 and 184.1, respectively, showing that the incidence of GMPs was not correlated with intratumoral microvessel density (P = 0.676). There was no correlation between vascular endothelial growth factor expression and the incidence of GMPs, but GMPs were more frequently seen in Ang-1-positive tumor than in Ang-1-negative tumor. The 5-year survival rate of GMP-positive patients was 54.2%, which was significantly lower than that of GMP-negative patients (72.3%; P = 0.016). The 5-year survival rate of higher-MVD patients (71.5%) seemed to be lower than that of the lower-MVD patients (63.7%), but the difference did not reach a statistical significance (P = 0.137). A multivariate analysis confirmed that the presence of GMPs was a significant prognostic factor (P = 0.003), whereas MVD was not. In conclusion, GMPs indicate an aggressive angiogenic phenotype associated with a poor prognosis in NSCLC.