Pathological risk factors for metastatic disease in patients with testicular non-seminomatous germ cell tumors are debated. The tumor-node-metastasis (TNM) classification eighth edition for testicular cancers includes divergent versions, by the International Union Against Cancer (UICC) and by the American Joint Committee for cancer (AJCC). We investigated pathological predictors of metastatic disease at presentation in 219 non-seminomatous germ cell tumors with reference to both classifications. Age, tumor size, percentage of embryonal carcinoma, lymphovascular invasion, invasion of stromal rete testis, hilar soft tissue, epididymis, spermatic cord, and tunica vaginalis, as well as tumor at spermatic cord margin, were assessed and correlated with clinical stage at presentation. Of the 219 NSGCT cases, 151 (69%) were clinical stage I, 68 (31%) were clinical stage II/III. On univariate analysis, tumor size (P = 0.028), percentage of embryonal carcinoma (P = 0.004), lymphovascular invasion (P = 0.001), stromal rete testis invasion (P = 0.001), hilar soft tissue invasion (P = 0.010), epididymis invasion (P = 0.010), direct spermatic cord invasion (P = 0.001), and tumor at spermatic cord margin ((P = 0.009) were associated with higher clinical stage. On multivariate analysis, lymphovascular invasion (P = 0.003), tumor size (P = 0.005), percentage of embryonal carcinoma (P = 0.005), stromal rete testis invasion (P = 0.008) remained significant. A tumor size of 6 cm and an embryonal carcinoma percentage of 70% were the significant cut-off values. We conclude that in addition to lymphovascular invasion, stromal rete testis invasion, tumor size, and embryonal carcinoma percentage are strong predictors of metastatic disease at presentation and their inclusion should be considered in any future TNM revision. Further, our results support the changes in the AJCC TNM eighth edition as invasion of the epididymis and hilar soft tissue were both univariately significant.