In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel. Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10% (by volume) of hexanol and 90% (by volume) neat cashew nut shell biodiesel was referred to as CNSBD900H100 and fuel comprising 20% (by volume) of hexanol and 80% (by volume) of neat cashew nut shell biodiesel was referred to as CNSBD800H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at 10% and 20% (by volume) to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.