A switchback design experiment with eight cows was used to evaluate wet corn distillers grains (33.9% dry matter) as a feed for lactating cows. All cows were fed corn silage ad libitum and 3.2kg of alfalfa hay daily. Cows on the control diet were fed an 18.6% crude protein concentrate mix of corn, oats, and soybean meal at 1 kg/2.5kg milk produced. Cows on the experimental diet were fed 13.6kg wet distillers grains (34% crude protein, dry) and a 10.9% crude protein concentrate mix of corn and oats at 1 kg/2.5kg milk produced in excess of 11kg milk daily. The reduced amount and reduced protein content of the concentrate mix fed to cows on the experimental ration was to compensate for protein and energy consumed as wet distillers grains. Cows averaged 12 wk postpartum at the start of the experiment, which consisted of three 4-wk periods. Cows fed control and wet distillers grains rations produced 27.0 and 27.6kg of milk daily. No differences in milk fat (3.44 and 3.41%), milk protein (3.09 and 3.10%), or total solids (12.1 and 12.16%) were observed. Total dry matter consumption was similar for control and wet distillers grains rations (20.3 and 20.8kg dry matter/day). Rumen volatile fatty acids, pH, and ammonia were similar for cows fed control and distillers grains rations. Wet distillers grain can be effective in rations for lactating dairy cattle as a protein and energy source.