Professional communication practices are not immune to the impact of transformations, which have become the daily life of organisations. The researcher analyses the evolution of mutations in communication practices and norms through the experiential stories of forty-five communication professionals, all active in Belgian organisations in the profit and non-profit sectors. The study includes three age demographics each with fifteen communicators and considers their professional socialisation along the timeframe continuum of pre-Internet through to the introduction of digital social platforms. The first part of the thesis debates the theory of institutionalisation and its central concepts. The researcher refers to the organisational field where the interpretation and adoption of practices are negotiated by actors whose interests may be competing and who activate the games of power and influence. The thesis also examines the carriers and pillars of isomorphic mechanisms and then discusses the communication profession and its professionalisation by exploring the institutional actors who contribute to this process by anchoring and legitimising the practice through professional associations and academic programmes. The second part successively presents the actors of the organisational environment who exert coercive, normative or mimetic pressures (macro), the organisational transformations which impact the role of communication (meso), and the function of communication professional as well as the professionalising trajectories in response to the injunctions analysed at the previous levels (macro and meso). The researcher interprets how the canvas of temporality punctuates the successive stages of professionalisation and institutionalisation at rates that correspond to the communicational maturity of organisations in Belgium. The study observes a generational effect in the strategies adopted in relation to the challenges posed by so-called agile organisational transformations, societal expectations and technological ...