Background: Serum microRNAs are candidate biomarkers for diagnosing and monitoring germ cell tumors (GCTs). The ability of miRNA to inform treatment in low-stage chemotherapy-naïve patients is unexplored. We sought to evaluate the performance characteristics of serum miRNA levels to predict viable GCT in chemotherapy-naïve patients undergoing primary retroperitoneal lymph node dissection (RPLND). Methods: We prospectively collected presurgical serum samples and clinicopathologic characteristics from consecutive chemotherapy-naïve GCT patients undergoing primary RPLND from 2016-2019. Serum miRNAs (-367-3p/-371a-3p/-372-3p/-373-3p/-375) were isolated and quantified. RPLND histopathology was categorized as benign, viable GCT, or teratoma; miRNA levels were compared among groups. Performance characteristics, including receiver operating characteristic (ROC) curves, assessed the discriminative ability of each miRNA signature to predict viable GCT. Results: 24 patients with stage I-II GCT underwent RPLND, revealing viable GCT in 11 (46%), teratoma in 3 (13%), and benign pathology in 10 (42%) patients. miR-371a-3p was the most discriminatory serum miRNA for viable GCT, exhibiting ~13,000-fold increase in expression over teratoma or benign pathology. On ROC analysis, miR-371a-3p had AUC = 0.965, with sensitivity and specificity of 100% and 92%, respectively. The AUC for other serum miRNAs in predicting viable GCT were 0.874 (miR-367-3p), 0.846 (miR-372-3p), and 0.720 (miR-373-3p). These serum miRNAs were not predictive of pure teratoma. Potential limitations include small cohort size and no post-RPLND sera for comparison. Conclusions: Serum miRNAs, particularly miR-371a-3p, can accurately differentiate small-volume viable GCT from benign processes or teratoma in patients with negative serum tumor markers undergoing primary RPLND. If validated, these data suggest a basis to implement precision medicine strategies in treating patients with early-stage GCT.