In this study, energy and exergy analysis were performed for a single cylinder, water-cooled diesel engine using biodiesel, diesel and bioethanol blends. Each experiment was performed at twelve different engine speeds between 1000 and 3000 rev/min at intervals of 200 rev/min for four different fuel blends. The fuel blends, prepared by mixing biodiesel and diesel in different proportions fuel with 5% bioethanol, are identified as D92B3E5 (92% diesel, 3% biodiesel and 5% bioethanol), D85B10E5 (85% diesel, 10% biodiesel and 5% bioethanol), D80B15E5(80% diesel, 15% biodiesel and 5% bioethanol) and D75B20E5 (75% diesel, 20% biodiesel and 5% bioethanol). The effect of blends on energy and exergy analysis was investigated for the different engine speeds and all the results were compared with effect of D100 reference fuel. The maximum thermal efficiencies obtained were 31.42% at 1500 rev/min for D100 and 31.42%, 28.68%, 28.1%, 28% and 27.18% at 1400 rev/min, respectively, for D92B3E5, D85B10E5, D80B15E5, D75B20E5. Maximum exergetic efficiencies were also obtained as 29.38%, 26.8%, 26.33%, 26.15% and 25.38%, respectively, for the abovementioned fuels. As a result of our analyses, it was determined that D100 fuel has a slightly higher thermal and exergetic efficiency than other fuel blends and all the results are quite close to each other.