Scenarios of serious games become more complex, highly interactive and hard to validate by humans due to the number of possible paths. Increasingly, authoring systems are proposed to support the designers in the scenario’s elaboration. These systems need tools to model and validate the interactive scenarios. But often, only testing activities with beta testers attempt to ensure the reliability of games’ scenarios, once the serious game is developped. Indeed, testing activities could reveal errors and bugs in the interactive scenario but they are not sufficient and not adapted to validate scenario in the design stage. To be of any real value, for any learning system, a scenario must verify properties. This paper addresses both the modeling and the validation of Interactive scenarios in the design stage of serious games. We aim to support authoring systems for scenarios, to verify serious game’s properties and thus to increase the design quality of serious game. We propose a formal framework to scenario’s modeling and validation in the design stage. First, we use Coloured Petri nets (CPN) as a modeling language. Then, the formal validation of the interactive scenario is performed by means of CPN Tools, an industrial-strength computer tool for analysing CPN models. Using CPN Tools, it is possible to investigate the behaviour of the modelled serious game using simulation and to verify properties by means of model checking.