Background: Traditional tumor markers for testicular germ cell tumor (TGCT), lactate dehydrogenase (LDH), beta-human chorionic gonadotropin (hCG), and alpha-fetoprotein (AFP), have limited sensitivity in detecting residual tumor on PC-RPLND. Micro-RNAs (miRNA) have emerged as a promising serum markers to predict residual TGCT on RPLND. Previous reports have suggested high levels of miRNA-375 in teratoma. The purpose of this study was to evaluate serum miRNA-375 as a tumor marker for PC-RPLND teratoma. Methods: We prospectively collected pre-surgical serum samples from consecutive GCT patients undergoing PC-RPLND. Serum miRNA-375-3p and -5p expression was validated and quantified by qPCR. Receiver operating characteristic (ROC) analysis and logistic regression were utilized to evaluate test characteristics and predictors of teratoma. Results: 40 patients underwent PC-RPLND. 18 had benign pathology, 2 viable TGCT, 19 teratoma, and 1 embryonal rhabdomyosarcoma. 3 miRNA specimens were excluded as outliers. miRNA-375-5p was undetectable in all samples examined. ROC analysis of miRNA-375-3p revealed an area under the curve of 0.503. Of 19 patients with teratoma, 16 had elevated miRNA-375-3p (84.2% sensitivity). 6/17 with benign pathology had normal mi-RNA-375-3p (35.3% specificity). 16/27 with positive tests harbored teratoma (59.3% positive predictive value). 6/9 with negative miRNA-375-3p had benign disease (66.7% negative predictive value). Univariate analysis demonstrated that clinical stage, pre-RPLND LDH, AFP, hCG, N/L ratio, and miRNA-375-3p were not significant predictors of teratoma. Conclusions: miRNA-375 does not predict teratoma on PC-RPLND. Tissue expression of miRNA-375 did not translate to serum expression in our study. Reliable predictors of teratoma on PC-RPLND remain elusive.