Purpose - This paper is an extension to a previous empirical study that modeled the process of innovation diffusion in Australian architectural and engineering design (AED) firms. The present study utilised explanatory case studies to assist in the verification of this empirical model, which depicted pathways that explain the role of enabling 'climate for innovation' constructs in determining the level of innovation diffusion outcomes, and subsequent business performance in Australian AED firms. Design/methodology/approach - This paper presents the latter of a two-stage sequential mixed method research design: (1) quantitative empirical study; and (2) qualitative explanatory case studies. Specifically, this stage extracted findings from five explanatory case studies using a qualitative pattern matching analysis technique. Interview-based data collected from the case studies were analysed to formulate the relationship patterns between constructs, which were then compared with those predicted by the empirical model. This approach afforded a determination on the extent to which the case-based findings (i.e. work-setting phenomena) explained (i.e. validated) the empirical model. Findings - The results of the case studies on five Australian AED firms indicated that the model could be adequately explained by the actual phenomena. This was evident in four of the cases providing a good to perfect match, and one showing a partial match, to the predicted patterns of relationships between the model constructs. Thus, the paper presents verified empirical pathways for AED firms, which suggested that, by increasing the level of leadership for innovation, the level of team climate and organisational culture for innovation can be improved. The improved culture for innovation would then heighten the level of innovation diffusion outcomes, which could, in turn, result in an enhanced business performance. Originality/value - This paper expanded and improved upon the current understanding of how the diffusion of innovation can be accelerated within the AED firm context. By focusing on the socio-psychological processes, the paper depicts the pathways to improved innovation diffusion outcomes and business performance, through fostering a robust climate for innovation. These pathways have been constructed empirically and were verified in this paper under real-work settings. Based on the validated model and the specific insights derived from the explanatory case studies, the paper also highlights a number of strategic implications for AED firms seeking to enhance their business performance through improving innovation diffusion practices. Keywords - Architectural and engineering design, Australia, explanatory case studies, innovation diffusion, pattern matching Paper type - Research paper