In this work, Niger seed oil biodiesel was tested as an emulsifier for diesel-ethanol (diesohol) blends at different percentage volumes. The blends of diesohol and Niger seed oil biodiesel were tested for its suitability in a CI engine. The biodiesel produced from Niger seed oil by transesterification process. It was found that all the fuel properties were within the specified ASTMD6751 standards. The research was aimed to study the performance of the diesel engine operating on diesel fuel as a baseline fuel and diesohol-biodiesel (DE5B10, DE10B10, DE15B10, DE5B20, DE10B20 and DE15B20) blends. The fuel blends were prepared with Niger seed oil biodiesel as an emulsifier with 10 (v/v%) and 20 (v/v%) of diesohol blends. The highest brake thermal efficiency was found with the blend DE15B10 (11.19% higher than diesel fuel) at maximum loading condition, and brake specific fuel consumption was found to be increased by 8.42%, 11.66% and 15.25% respectively with the blends DE5B20, DE10B20 and DE15B20 in comparison with diesel along with lower fuel consumption and decreased emissions compared to diesel fuel. The study revealed that diesohol-biodiesel blends can be employed as a alternative fuel for existing unmodified diesel engines due to its improved emission and performance characteristics. (C) 2020 Published by Elsevier Ltd.