Simulation, a new tool in teacher education programmes, requires further evidence as to its effectiveness in supporting the development of preservice teachers’ (PSTs’) mathematical discourse. The study explores the discourse of a group of preservice teachers while teaching the concept of volume in a simulation setting. Specifically, PSTs’ verbal interactions with virtual students (i.e. avatars) are examined using utterances as the basic unit of analysis. By applying mathematics discourse frameworks, the PSTs’ discourse was categorised, identified as different types and analysed both quantitatively and qualitatively. The findings reveal the dynamics of PSTs’ discourse and highlight how simulations provide an authentic classroom-like environment, with the potential to elicit PSTs’ mathematical discourse, including preparation for unexpected situations and fostering inclusive pedagogy. This article makes a contribution to the current literature by exploring the effectiveness of simulation-based teacher education programmes in developing preservice teachers’ (PSTs’) mathematical discourse skills. Specifically, the discussion offers valuable insights into the potential of simulations as a platform for preparing PSTs to become confident and competent educators capable of fostering inclusive learning communities.