Corncob molasses, a waste by-product in xylitol production, contains high concentrations of mixed sugars. In the present study, corncob molasses was used to produce 2,3-butanediol (BD) using Klebsiella pneumoniae SDM. This was the first report on the use of corncob molasses to produce bulk chemicals. Our results indicated that K. pneumoniae SDM can utilize various sugars contained in the corncob molasses in a preferential manner: glucose > arabinose > xylose. It was shown that high sugars concentration had an inhibitory effect on the cells growth and BD production. The maximum concentration of BD was 78.9 g/l after 61 h of fed-batch fermentation, giving a BD productivity of 1.3 g/l h and a yield of 81.4%. The present study suggests that the low-cost corncob molasses could be used as an alternative substrate for the production of BD by K. pneumoniae SDM, as well as a potential carbon source for production of other high-value chemicals.