Nowadays, managers face serious tasks, problems and challenges that require a fully engaged workforce. However, it has been found that only thirty percent of employees around the world are engaged in their job. Gamification –defined as the use of game elements and game-design techniques in non-game contexts- can increase engagement by fostering employees’ intrinsic motivation. Therefore, the aim of this thesis is to identify the key determinants for internal gamification to successfully enhance employee engagement. Following a Ground Theory approach, five semi-structured interviews with gamification experts were analyzed and coded into categories. Five categories of key determinants that contribute to a successful gamification design emerged: clear objectives, user-centred approach, context alignment, evolving design and intrinsic motivation. These key determinants were subsequently assessed by comparing them with the current body of literature on gamification, resulting in a concise and coherent framework of managerial implications. In addition, this approach allowed to identify discrepancies between researchers and entrepreneurs regarding their knowledge on gamification.