Successful training transfer is necessary for employees to adapt to this fast-changing working world. In this study, we investigate whether transformational trainer behaviour can inspire training participants to change their self-concept during training and whether this is related to increased training transfer. Following the self-concept based theory, we examine the relationship between transformational trainer behaviour and training transfer, mediated by psychological empowerment. Moreover, we test a cross-level interaction such that the indirect effect varies based on the number of participants per training group. We conducted a two-wave study with 373 training participants in 58 training groups. Multilevel moderated mediation analysis showed that the training participants' psychological empowerment mediated the positive relationship between transformational trainer behaviour and training transfer two months later. However, this indirect effect was not moderated by the number of participants per group. These results add to the discourse on the importance of trainers for training transfer and offer a new perspective on training as changing the participants' self-concept.