In their traditional role as 'bean-counters℗þ, 'scorekeepers℗þ and 'controllers℗þ, management accountants were frequently excluded from operational decision-making. Criticism by operational managers about management accountants℗þ decisions-making behaviour included that management accountants preferred evidence-based decisions, as opposed to the intuitive decisions that were regularly required in the business management environment. However, the role of management accounting professionals are changing to that of business partner. The first aspect which the study investigated was whether management accounting professionals experienced an increase in their involvement in business-related decision-making, as suggested by their emerging business partner role. Psychology-related behavioural aspects, which may result in biased decision-making, play a definite role in decision-making behaviour where the use of intuition is required. A review of literature indicated that management accounting professionals were less comfortable with making intuitive decisions. Therefore, they could be particularly susceptible to decision biases related to the influence of behavioural aspects. Accordingly, the second aspect which the study investigated was the susceptibility of management accountants to the main behavioural decision biases related to the use of decision heuristics and the effects of frame dependence. A survey design was employed to investigate decision-making involvement and susceptibility to behavioural biases by means of an electronic questionnaire. Responses were received from an international sample of management accounting professionals, including members of the Institute of Management Accountants (USA) and the Chartered Institute of Management Accountants (UK). The responses were analysed quantitatively, using both univariate and multivariate statistics. The study extends the current body of knowledge by being the first to comprehensively investigate the presence of behavioural biases in the decision-making behaviour of management accounting professionals as a group of decision-makers, which is especially relevant due to their changing decision-making role in organisations. Additionally, contrary to many previous studies in the behavioural decision-making field, the study focused on an international, widely dispersed, sample of professionally employed decision-makers. The study also contributes to the debate on the conflict in findings regarding the prevalence of the changing role of the management accountant. The important findings of the study were as follows: AÌ2℗ʺ Management accounting professionals were involved in making business-related decisions. However, this involvement varied depending on the position in which a management accounting professional was employed, and the size of the company in which the professional was employed. The findings regarding the decision-making involvement of management accounting professionals also indicated that the promulgated business partner role was not as pervasive as suggested by most of the literature. AÌ2℗ʺ Management accounting professionals experienced an increase in business decision-making involvement. This experience was not as widespread as the literature on the business partner role suggests, and was more pronounced for professionals between 30 and 49 years of age, and those more amenable to using their judgement when making decisions. AÌ2℗ʺ Management accounting professionals were susceptible to frame dependence bias. The susceptibility of management accounting professionals to the biases of concurrent decisions framing, the certainty effect and the pseudo-certainty effect was similar to that of other populations. However, these professionals exhibited a lower susceptibility to loss aversion bias. Their susceptibility to mental accounting bias requires further investigation. AÌ2℗ʺ Management accounting professionals were also susceptible to heuristic-based bias. Their susceptibility was similar to that of other populations for the representativeness-related confirmation bias, as well as for the adjustment and anchoring heuristic-related bias. Management accounting professionals exhibited lower susceptibility than other populations to the biases of misconceptions of chance, misconceptions of regression to the mean, general overconfidence, and affect. However, they were more susceptible to overconfidence in performing difficult tasks than other populations. The findings could be of value to the management accounting profession in indicating that educational requirements existed for both the traditional and emerging roles of the management accountant. The study also initiated the research into the susceptibility of management accounting professionals to behavioural biases and paved the way for research and other actions aimed to debias the decision-making behaviour of these professionals.