Behavioural design has emerged as an important domain of design practice and research due to its ability to deliver the desired outcomes beyond technical designs. Research on behavioural design is not successful in discerning it from other design domains, which is important for theory building. This paper discerns the unique characters of behavioural design by tracing the emergence of behaviour in design. Twelve interviews from six behaviour design cases belonging to four firms has been used to further discern the unique characteristics resulting into the conceptual model of behavioural design