Legislation concerning the pollutant emissions of diesel passenger cars is becoming increasingly restrictive, especially for nitrogen oxide (NOx) and particulate matter (PM). A methodology that combined physical approach and a dynamic output feedback based observer for the modelling and estimation of the pollutant emissions in diesel engines is thus proposed. A grey box control-oriented model of NOx emissions is developed; this model was designed based on a deep analysis of the crank-angle discrete combustion process of the test-bench diesel engine. This model will be used to help the understanding of the thermal NOx emission formation process. It provides the basics for the further development of the diesel engine emissions control-oriented models, but it couldn't be used to predict real-time pollutant emissions on a vehicle. The model is calibrated by experimental measurements and a complete cylinder pressure and temperature analysis. Then, to solve the vehicle integration problem (real-time calculation problem) this model and a linear model of the diesel engine were used to develop an dynamic observer to estimate the quantities of particulate matter.