The fuel efficiency and emission reductions are the two consistent drivers for diesel engine development. Although many control devices mounted in diesel engine and in addition to the development of individual emission control methods, optimization techniques are required to utilize these methods in finding optimal engine operating conditions efficiently. This research was focused on the minimization of nitrogen oxides (NOx) emission and soot emission, as well as improving brake specific fuel consumption (BSFC) and power in a single cylinder diesel engine, which can be modeled as a multi-objective optimization problem. Many approaches have been applied to multi-objective optimization problems. In recent years, particle swarm optimization (PSO) method has been successfully applied to different areas since its advent. It has been demonstrated that PSO is an effective method for optimization problem.