The aim of this study was to examine the differential effects of specific types of supervisor support on transfer of training, taking into account established trainee characteristics, such as trainees' motivation to learn, motivation to transfer, and training self-efficacy. More specifically, nine types of supervisor support were examined (pre-training information, role modelling & facilitation, request sharing, favourable attitude, coaching & feedback, openness, involvement & accountability, work coverage, and training participation). In addition, the mediating effect of training retention is explored, as learning outcomes may present an intervening variable that connects supervisor support to transfer of training. A time-lagged design was used to investigate the relationships in the proposed model and it was evaluated using partial least squares path modelling (PLS-PM). Data was gathered in Belgium through online questionnaires at three points in time from 111 participants of work-related training. Participants were employees from a retail organisation and different government agencies. Results indicate that only supervisors' accountability and involvement positively predicted employees' transfer of training three months after training. In addition, it was found that supervisors' involvement and accountability had an indirect effect on transfer of training through training retention.