Contributions to the family firm literature have given attention to different challenges that family firms have to face in their life cycle when organisational complexity increases and managerial processes are required. This paper investigates how management accounting (MA) tools enable family and managerial views of doing business to complement each other during the professionalisation process. In particular, the paper discusses a longitudinal case study on a family firm’s professionalisation, when an external advisor introduced financial ratio analysis and contribution margin reports. The case evidence shows that MA tools, by facilitating communication amongst family firm members and the external advisor, favours the complementing between family firm and managerial views of doing business during the professionalisation process. When simultaneously trusting family firm and managerial views of doing business, family firm members had the chance to interpret business facts differently, discovering new business opportunities. The paper contributes to the family business literature examining the professionalisation process through the pragmatic constructivist (PC) perspective that analyses the main traits of family firm and managerial views of doing business, stressing the relevance of values in interpreting business facts and in identifying factual possibilities. On this issue, the PC perspective is useful in understanding the role of MA tools as a communication basis for enabling the complementing of different views of doing business during the professionalisation process.