Supporting undergraduate students with their academic literacies has recently been a major focus in higher education in the UK. This paper explores the value of tutor mediation in the context of academic writing development among undergraduate business studies students in open and distance learning, following the dynamic assessment (DA) approach that has been developed within Vygotskian sociocultural theory of learning (Vygotsky, 1978). DA is an assessment approach that blends instruction and assessment. The data, which came from a pilot study of a larger research project, consisted of text-based interaction between a tutor-researcher and two business studies students across various drafts of two assignments in line with the DA approach. This interaction was mediated by computers mainly through emails. The analyses of such interaction suggest that DA can help to identify and respond to the areas that students need the most support in (in this study, managing information flow). Finally, we argue that a learning theory-driven approach such as DA can contribute to undergraduate students' academic writing development by responding to their individual needs. (Contains 3 tables and 6 figures.)