The adaptation and implementation of management accounting/Controlling in the public sector was only partially carried out (this has been noted, e.g., by Hirsch, Nitzl & Schauß (2015); Nuhu, Baird & Appuhami, (2017)), and those implementations that were completed exhibited only limited success. In particular, in Germany, the impact of the implementation efforts of controlling has been disappointing. The complexity of implementations of management accounting/Controlling (as noted, e.g., by Granlund, 2001; Gosselin, 1997; Baxter & Chua, 2003) is even more pronounced in public institutions due to the social and political context than in private sector organisations (Hoque, 2014). Implementation barriers, particularly on a personal level in the form of resistance, persistently make an introduction more difficult. The underlying reasons for resistance have been studied just as little (Parvis-Trevisany, 2006; Agasiisti, Catalano & Erbacci, 2018) as the behavioural science aspects impacting the behaviour of actors in the implementation (Parvis-Trevisany, 2006). Hence, there is a need to study particularly the specific motives and behavioural aspects of actors in the public sector (Hoque, 2014); this thesis meets this demand and aims to examine implementation barriers as well as aspects of and reasons for resistance in greater depth. The empirical study is based on the introduction of a complete controlling concept during the refugee crisis. The empirical foundation of the case study involved a combination of interviews and participant observations. They were supplemented by expert interviews in order to increase the significance of the results and to make a comparison of a problematic with a successful introduction. The thesis examines resistance and its triggers on the basis of behavioural reasoning theory and combines it with behavioural science approaches, including cognitive limitations of the individual actors. The resistances and triggers identified in the case study extend the behavioural reasoning theory with additional 'reasons against' for the introduction of management accounting/Controlling. In the case study, the following 'reasons against' were identified: (1.) fear of transparency, (2.) faulty understanding of Controlling (Controlling as monitoring (‘Kontrolle’)), (3.) overwhelming due to insufficient learning process and (4.) overwhelming due to overambitious targets. The resistance behaviour can be explained by cognitive limitations. For example, the phenomena of overly ambitious targets is influenced by the cognitive limitations of the implementing actor in the form of availability and representativeness heuristics as well as anchor effects. In addition, the role of cognitive dissonance and information overload in the implementation process is highlighted and used as an explanatory approach for the resistance that occurs. The study shows also that different resistance behaviours occur under identical conditions.