The interaction between institutions and how this interaction can be studied and understood, dating back thousands of years, has emerged throughout history through various thinkers [1]. The complexity of today’s world is increasing, thus becoming a factor that generates organisations with characteristics that are distinct from those of the past. It is up to human beings to keep up with this complexity and analyse the phenomena that result from these organisations [2].

The constant evolution of society generates a permanent need for adaptation and evolution in the world in general, and in public administration in particular [2]. Despite the peculiarities and distinctive features surrounding the reforms that public administration has been undergoing, it is widely accepted that the Weberian model has lost momentum, giving way to new paradigms ^[3][4][3,4].

Arguing that institutional theory underpins research in various sciences due to its flexible nature and explanatory power [2], given the subject under study, it is important to note that institutions have always been a central focus for the social sciences [1].

Organisations were recognised as a social phenomenon as far back as the 1940s. In 1977, Meyer and Rowan published an article (Institutionalised Organisations: Formal Structure as Myth and Ceremony) that would come to be recognised as a milestone in the history of organisational analysis. The authors argued that institutional environments influenced the structures of many organisations [5].

The diversification and complexity of relations between the outside world and organisations is a result of the increased variability of the vectors that constitute them. The increase in constraints to which organisations are subject requires them to have an adequate and valid response capacity as a mechanism for adaptation and response. In this sense, the evolution of management/administration models are a reference for institutional theory when seeking to understand the social phenomena of organisations [6].

Given that organisational theory focuses on the relationship between the organisation and its environment as a factor that “adapts” its actions, it is important to understand how this environment determines the effectiveness, survival and need for evolution of the organisation [7]. An organisation that wants to remain “alive” in the labour market will inevitably have to face external and internal pressures (mostly external). In this sense, there is a need to legitimise itself so that its actions are “desired or appropriate within a socially constructed system of norms, values, beliefs and definitions” [8] (p. 574). However, for organisations to gain legitimacy within a context, they need to gain credibility and acceptance from their peers, which leads them to come closer together and converge. This process of approximation and convergence is known in the literature as isomorphism. This concept is defined as “the process that causes a unity of behaviour in various organisations operating in the same field and under the same environmental conditions” [7] (p. 95).

Thus, this entry article was created with the aim of sharing knowledge and enriching the topic under study. Regarding the adopted structure, this article addresses the literature on the concept of isomorphism, referencing the topic: from rationality and bureaucracy to isomorphism. It presents the contextualization of institutional theory, addresses the three major institutional currents and the new institutionalism, and finally, addresses the topic of the institutionalization of public administration. Conclusions, limitations, and proposals for future research are presented. Emphasising the aspects that isomorphism provides to organisations in the social environment in which they operate. In this way, the contributions of this research play a role in promoting and expanding scientific knowledge about isomorphism in public administration in general.

Despite the contributions of our article, limitations (gaps) were identified, namely the fact that although the contribution of academics offers important opportunities for knowledge exchange and multidisciplinarity in various areas of knowledge, it is important to mention that the variety of approaches and assumptions, which are sometimes ambiguous and self-contradictory, limits academic discourse and academic progress on this topic.

In conclusion, we note that, in light of the theoretical concepts discussed throughout this paper, there is a need to advance institutional theory in public administration based on isomorphism, with the aim of enabling, through the four points discussed above, the study, reinforcement and sharing of knowledge about the need for organisations to follow the most successful organisations (with highly professionalised resources) within the same sector as a ‘model,’ leading them to converge and become similar, a process known as isomorphism.