Enhanced tubular reabsorption of salt is important in the pathogenesis of obesity-related hypertension but the mechanisms remain poorly defined. To identify changes in regulation of salt transporters in the kidney, C57BL/6 mice were fed 40% (high fat, HFD) or 12% (control, CD) fat diets for 14 weeks. Compared with controls, HFD mice had significantly greater elevations in weight, blood pressure, and serum insulin and leptin levels. Examining sodium transporter expression, NKCC2 was unchanged in whole kidney and reduced in the cortex; NCC and α- and -ENaC were unchanged; β-ENaC was reduced. Phosphorylation of NCC was unaltered. Activating phosphorylation of NKCC2 at S126 was increased 2.5-fold. Activation of SPAK/OSR-1 was increased in kidneys from HFD mice and enhanced phosphorylation of NKCC2 at T96/T101 was evident in the cortex. Increased activity of NKCC2 in vivo was confirmed with diuretic studies. HFD mice had reduced activating phosphorylation of AMPK in the renal cortex. In vitro, activation of AMPK led to a reduction in pSPAK/pOSR1 in MEF-AMPK^+/+ cells, but no effect was seen in MEF-AMPK-/- cells, indicating an AMPK-mediated effect. Activation of the WNK/SPAK/OSR1 pathway with low sodium chloride solution invoked a greater elevation in pSPAK/pOSR1 in MEF-AMPK^-/- cells than MEF-AMPK^+/+ cells, consistent with a negative regulatory effect of AMPK on SPAK/OSR1 phosphorylation. In conclusion, this study identifies increased phosphorylation of NKCC2 on S126 as a hitherto unrecognized mediator of enhanced sodium reabsorption in obesity, and identifies a new role for AMPK in regulating the activity of SPAK/OSR1.