In this work, the development and the assessment of a real-driving capable co-simulation tool are performed. The co-simulation tool includes: an engine plant model, a simplified Electronic Control Unit (ECU) model, an external emissions model and an aftertreatment model. The co-simulation tool was developed and validated in each single sub-model as well as in its entirety. The validation was performed against real vehicle data on several driving cycles of WLTC and real-driving type. Based on the validation on the driving cycles, the co-simulation tool seems able to predict the general trends of the engine emissions and performances in real-driving conditions. In addition, this validation shows that the tool has the same behaviour in most of the driving cycles.