The past decades have witnessed the proliferation of research on knowledge work. Knowledge work has mostly been used as an antonym to manual work, to refer to specific occupations characterized by an emphasis on specialized skills and the use of theoretical knowledge. The efforts to encompass all the different contexts where knowledge plays a relevant role in work tasks has resulted in various and ambiguous definitions of what knowledge work actually is. In order to shed light on the elusive concept of knowledge work, we studied how it has appeared in the scientific discussion, and diffused from one scientific community to another. As the circulation of new ideas and concepts in scientific discussion is apparent through academic literature, we examined the emergence and diffusion of the concept of knowledge work through a citation analysis on articles from the Social Sciences Citation Index. The data set consists of 273 articles with 7,057 cited references for the 1974 to 2003 period, and we used a dense sub‑network grouping algorithm on the co‑citation network to distinguish highly cited groups of references. We distinguish three periods of diffusion of the concept of knowledge work. The results show that Drucker's In the age of discontinuity (1969) and Bell's The coming of post‑industrial society (1968) were the main influencers when the concept emerged in the scientific discussion from 1974 to 1992. After this period, we can distinguish a slow diffusion period from 1993 to 2003, when the concept started to gain attention, and a fast diffusion period from 1999 to 2003, when the research proliferated. The discussion dispersed outside the management domain already in the emergence period, but the management domain has stayed the main domain of discussion also later on. However, from 1992 to 2003 the discussion inside the management domain dispersed into different groups. One of the main influences to a new group of research that appeared at this time was Zuboff's In the age of the smart machine (1984). This group, drawing on research conducted on knowledge‑intensive firms, has recently produced highly cited articles such as Blackler's 'Knowledge, knowledge work and organizations' in Organization Studies (1995). As the current discussion on knowledge work is dispersed in different groups, there is a need to engage in a common conceptual discussion and define what is actually meant by knowledge work.