Digital innovations are rapidly diffusing within the construction sector. With the UK government policy mandating building information modelling (BIM) by 2016, engineering firms are faced with challenges related to embedding new technologies and associated working practices for the digital delivery of major infrastructure projects. Drawing from diffusion of innovations theory, this research attempts to answer the question of: how digital innovation diffuses in the firm? It adopts a contextualist approach through in-depth case study of a large and international engineering project-based firm. The analysis of the empirical data, which was collected over four years of close interaction with the firm, provides a narrative for the diffusion of the digital innovation across the firm where both the innovation and the firm were in flux. The diffusion process has evolved through three main mechanisms: centralisation of technology management, standardisation of digital working practices, and globalisation of digital resources. This case has both theoretical and practical implications; it describes the diffusion of a digital innovation in a complex social system. This extends diffusion of innovations studies in construction, and guide engineering firms in their efforts to adopt and implement new innovations.