The present experimental study was carried out to investigate the performance and the exhaust emission characteristics of a single cylinder diesel engine using different dose levels of multiwall carbon nanotube additives (MWCNT) and JME-diesel fuel mixture (JB20D). The tests were conducted at various engine loads and variable engine speeds. The MWCNT nanoparticles were mixed with the JME-diesel blended fuel with variable mass fractions in the range from 10 to 50 mg/l. Results of the present study showed that the recommended fuel blend JB20D slightly decreased the engine performance and increased exhaust emissions for all operating conditions. The use of nano-additives was found to improve all engine performance parameters for the studied dose levels. However, the best emission characteristics (reduction in NOx by 45 %, CO by 50 %, and UHC (Unburned Hydrocarbons) by 60 %) were achieved with a dose level of 20 mg/l while the best mechanical performance (reduction in BSFC by about 15 %) was attained at a dose level of 40 mg/l compared with the corresponding values obtained when only a blended fuel of 20% biodiesel was used. The recommend dose level of MWCNT additives to achieve significant improvement in engine performance parameters was estimated to be 30 mg/l.