The goal of this study is to verify the presence of the three types of isomorphic mechanisms (mimetic, coercive and normative) of the New Institutional Sociology (NIS) in accountancy firms.A descriptive research with a quantitative approach was conducted, through a survey with a sample of 122 accounting firms in the Brazilian State of Santa Catarina.The survey results show that in the accounting firms in the regions of Florianópolis, Western Santa Catarina and the Serra Catarinense, the mimetic isomorphism predominated, while in the North and South of the state and Vale do Itajaí region, coercive isomorphism prevailed.Normative isomorphism was not prevalent among the other regions, but had a strong influence in the Southern region of Santa Catarina.The Serra Catarinense presented the highest number of firms with ratios that deviated from the average rate found for each type of isomorphism; and the Vale do Itajaí region had few firms that deviated from the average rate.In general, all the regions showed e(d i ) close to 1, i.e. there was little deviation of the isomorphism rates compared to the averages found.It is concluded that in the firms studied, all three isomorphic mechanisms types of the New Institutional Sociology are present, to a greater or lesser extent. KeyworDs: