In this study, combustion characteristics and nano-size soot particle emissions from a stationary conventional diesel engine have been experimentally investigated using butanol/diesel blends. Experiments were conducted on a single cylinder stationary diesel engine at a constant speed of 1500 rpm for neat diesel and butanol/diesel blends (i.e., 10%, 20% and 30% butanol on volume basis) at different engine loads. Piezoelectric pressure transducer installed in the engine combustion chamber was used for measuring cylinder pressure data. In-cylinder pressure data for 2000 consecutive engine cycles was recorded and averaged data was used for the analysis of combustion characteristics. Butanol/diesel blends show higher rate of heat release in comparison to neat diesel and heat release rate increases with butanol percentage in the blend. Opacity meter and exhaust particle sizer were used for analyzing smoke opacity, size and mass distributions of soot particles respectively at different engine operating conditions. Soot particle distribution from 5 nm to 1000 nm was recorded at each test condition. Results show that total particle concentration decreases with an increase in engine operating loads. It was found that butanol/diesel blends have lower total particulate concentration and the surface area.