Internal combustion engine comprising a device for estimating pollutant emissions, the estimating device being configured to calculate a first value (Pollut) of pollutant emissions by taking into consideration the rotational speed of the engine, a measured temperature for the coolant circulating through the engine, a fuel consumption (Qfuel) of the engine, an estimated value indicative of the richness of the gases entering the cylinders of the engine, and an engine ignition advance (φ), the said estimating device being configured to calculate at least one value (Pollut) chosen from: - a first value (Pollut) of nitrogen oxides emissions as being the product of a first refined function of the fuel consumption (Qfuel), of a second refined function of the ignition advance (φ), of a third refined function of the coolant temperature, and of a negative exponential term of a power of the richness of gas entering the cylinders, - a second value (Pollut) for carbon monoxide emissions as being the product of a refined function of the coolant temperature times the fuel consumption (Qfuel) of the engine, and times a refined function of the richness of the gases entering the cylinders of the engine, and - a third value (Pollut) for emissions of incompletely burnt hydrocarbons as being a product of a refined function of the ignition advance (φ), times a refined function of the coolant temperature, both multiplied by a first second degree polynomial function of the inverse of the rotational speed of the engine, by a second second-degree polynomial function of the richness, and by a third second-degree polynomial function of a reduced variable, the reduced variable being proportional to the flow rate (Qair, Qair_mgc) of air entering the engine and the temperature (Tman) of the gases in the inlet manifold and inversely proportional to the pressure (Pman) of the gases in the inlet manifold of the engine, and in which, if the estimating device is configured to calculate the said third value (Pollut), the estimating device is further connected to a sensor of pressure (Pman) in an inlet manifold of the engine and to a sensor of temperature (Tman) of the gases in the inlet manifold of the engine, and to a means of estimating the rotational speed of the engine and to a means of estimating the flow rate (Qair, Qair_mgc) of air entering the engine. - a first value (Pollut) of nitrogen oxides emissions as being the product of a first refined function of the fuel consumption (Qfuel), of a second refined function of the ignition advance (φ), of a third refined function of the coolant temperature, and of a negative exponential term of a power of the richness of gas entering the cylinders, - a second value (Pollut) for carbon monoxide emissions as being the product of a refined function of the coolant temperature times the fuel consumption (Qfuel) of the engine, and times a refined function of the richness of the gases entering the cylinders of the engine, and - a third value (Pollut) for emissions of incompletely burnt hydrocarbons as being a product of a refined function of the ignition advance (φ), times a refined function of the coolant temperature, both multiplied by a first second degree polynomial function of the inverse of the rotational speed of the engine, by a second second-degree polynomial function of the richness, and by a third second-degree polynomial function of a reduced variable, the reduced variable being proportional to the flow rate (Qair, Qair_mgc) of air entering the engine and the temperature (Tman) of the gases in the inlet manifold and inversely proportional to the pressure (Pman) of the gases in the inlet manifold of the engine, and in which, if the estimating device is configured to calculate the said third value (Pollut), the estimating device is further connected to a sensor of pressure (Pman) in an inlet manifold of the engine and to a sensor of temperature (Tman) of the gases in the inlet manifold of the engine, and to a means of estimating the rotational speed of the engine and to a means of estimating the flow rate (Qair, Qair_mgc) of air entering the engine.