Shape of combustion chamber plays a major role in controlling of combustion process and emission mechanisms occurring inside the combustion chamber. To implement ideal combustion chamber facilitates are essential to meet emission norms. In this context, an experimental investigation were carried out on a single cylinder four stroke direct injection diesel engine operated in dual fuel mode using Rice bran oil methyl ester (ROME) and Coconut shell wood derived producer gas. ROME is used as a pilot injected fuel which ignites the producer gas and air mixture when subjected to higher compression ratio. In the present work, different combustion chamber shapes were designed and developed by keeping the same compression ratio of existing diesel engine. The engine makes use of the hemispherical combustion chamber (HCC) shape. In order to study the effect of other combustion chamber shapes on the performance of dual fuel engine, Cylindrical (CCC), Trapezoidal (TrCC), and Toroidal combustion chamber (TCC) shapes were used. Various engine parameters such as power, torque, fuel consumption, and exhaust temperature, combustion parameters such as heat release rate, ignition delay, combustion duration, and exhaust emissions such as smoke opacity, hydrocarbon, CO, and NOx, were measured. Results revealed that the TCC shape resulted in overall improved performance with reduced emission levels compared to other shapes tested. Total hydrocarbon emission (THC) and carbon monoxide (CO) were also decreased significantly compared to other combustion chambers tested. Results reveal that more information may be positive in terms of improvement in exhaust emissions. Nevertheless, some positive conclusions have been reached for TCC as a result of this work.