The efficient co-fermentation of glucose and xylose is necessary for the economically feasible bioethanol production from lignocellulosic biomass. Even with xylose utilizing Saccharomyces cerevisiae, the efficiency of the lignocellulosic ethanol production remains suboptimal mainly due to the low conversion yield of xylose to ethanol. In this study, we evaluated the co-fermentation performances of SXA-R2P-E, a recently engineered isomerase-based xylose utilizing strain, in mixed sugars and in lignocellulosic hydrolysates. In a high-sugar fermentation with 70 g/L of glucose and 40 g/L of xylose, SXA-R2P-E produced 50 g/L of ethanol with an yield of 0.43 g ethanol/g sugars at 72 h. From dilute acid-pretreated hydrolysates of rice straw and hardwood (oak), the strain produced 18–21 g/L of ethanol with among the highest yield of 0.43–0.46 g ethanol/g sugars ever reported. This study shows a highly promising potential of a xylose isomerase-expressing strain as an industrially relevant ethanol producer from lignocellulosic hydrolysates.