The period following Hosni Mubarak’s resignation can be analysed as a ‘revolutionary situation’ without a ‘revolutionary outcome’ (Ch.Tilly) or as a ‘failed transition’ (Nathan Brown) during which several actors were in competition for power and for defining new rules for the political game (A.Boutaleb, S. BenNefissa). My paper aims to provide a new theoretical framework in order to analyse this struggle for power through the lens of legitimacy. Though, rather than analysing the narratives of each actors I intend to focus on modes of legitimation as praxis. Indeed, while the 2011 uprising can be defined as a ‘crisis of legitimation’ (M.Camau), the transition that followed can be analysed as a process of legitimation. My paper based on my doctoral researches (observation’s fieldwork) aims to demonstrate that the institutional process has lost its legitimacy because of competing claims using competing modes of legitimation. It provides a conceptual framework of the use of legitimation by the actors (rulers and challengers) during the transition in order to defend their claims over power. It shows that such a competition for legitimacy was witnessed in each decisive moment of the transition (when the ruling coalition may change). The lack of consensus around the institutional process set up by the army fostered the actors to advance competing claims for which they used various modes of legitimation. In this struggle indeed, competitors have been prone to legitimating their own claims through revolutionary mobilisation, electoral conquest, judicial verdicts or constitutional materials. What makes this process specific is the ‘political crisis’ (M.Dobry) and the lack of hierarchy between those modes of legitimation (in ‘normal’ times, the electoral process should take precedence over the popular mobilisation). Moreover, each mode of legitimation is not exclusively used by certain actors insofar as they all tried to handle various modes of legitimation. Eventually, the electoral process which has been widely considered as fair and free did not succeed in bringing to power a legitimated ruler. On the contrary, the military coup has been supported by a wide range of the political spectrum as well as by many within the population. In the end, while some scholars favour the thesis of a ‘counter revolution’, my research shows that the coup was the result of a process of legitimation in which the revolutionary legitimation prevailed over the electoral legitimation.