As miR-137 is a regulator of aquaporin-2 (AQP2) expression and TNF inhibits the expression of several extrarenal aquaporins, we tested the hypothesis that TNF inhibits AQP2 in the kidney via a miR-137-dependent mechanism. AQP2 mRNA and protein expression decreased approximately 70% and 53%, respectively, in primary renal inner medullary collecting duct (IMCD) cells transfected with a miRNA mimic of mmu-miR-137, suggesting that miR-137 directly targets AQP2 mRNA in these cells. Exposure of IMCD cells for 2 h to 400 mosmol/kg H2O medium increased mmu-miR-137 mRNA expression about 2-fold, conditions that also increased TNF production approximately 4-fold. To determine if the increase in mmu-miR-137 mRNA expression was related to the concomitant increase in TNF, IMCD cells were transfected with a lentivirus construct to silence TNF. This construct decreased mmu-miR-137 mRNA expression by approximately 63% suggesting that TNF upregulates expression of miR-137. The levels of miR-137 also increased approximately 2-fold in IMCD tubules isolated from male mice given 1% NaCl in the drinking water for 3 days. Intrarenal lentivirus silencing of TNF increased AQP2 mRNA levels and protein expression concomitant with a decrease in miR-137 levels in tubules isolated from mice given NaCl. The changes in AQP2 expression levels affected the diluting ability of the kidney, which was assessed by measuring urine osmolality and urine volume, as the decrease in these parameters after renal silencing of TNF was prevented upon intrarenal administration of miR-137. The study reveals a new TNF function via a miR-137-dependent mechanism that regulates AQP2 regulation expression and function.