The aim of the paper is to explore a possible theoretical foundation for the `work system approach'. The concept of work systems has been suggested as the core object of study in the field of information systems. The scope of the work system approach is determined by pragmatic relevance and high comprehensibility, with the goal of being applicable for professionals in both IT and business as well as IS researchers. This approach has, however, been criticized for having theoretical shortcomings. In this paper, a theoretical foundation is suggested and explored by relating it to work practice theory and its roots in socio-instrumental pragmatism. The results show that it is both possible and fruitful to ground the work system approach theoretically in socio-instrumental actions.