Serious Games (SG) have a particular ability to motivate and engage in the therapeutic and learning process. There are multiple approaches based on methodologies, frameworks, and models for SG design, which have been proposed based on a specific domain. However, the relationship between the Software Engineering methodologies, with the requirement described in the Game Design Document, and the Instructional Design have not been discussed together. This paper proposes a conceptual model and discusses their relations among those domains, that aims to fill this gap. In order to define the model, those approaches available were analyzed and compared, then suggests several components needed for game design. It describes the primary structure focus on four phases Analysis, Design, Development, and Evaluation, which identifies and validates the roles of all components to achieve the desired educational goals. SG maned ''ATHYNOS'' was developed to help children with learning disabilities. Finally, a case study with three units of analysis points out that ATYHNOS aided participants in the level of concentration, hand-eye coordination, motor skills, and cognitive reinforcement. INDEX TERMS Serious games, conceptual model for design, game-based learning, ATHYNOS.