Purpose: The impact of the number of coworkers participating in training on transfer outcomes has largely been overlooked. This paper aims to examine whether the number of coworkers participating in training interacts with peer support (PS) to influence training motivation and transfer. Design/methodology/approach: Data were collected using a cross-sectional survey from a sample of 688 employees working in 14 midsize and large companies. All participants were recent trainees in various open skill (e.g. leadership) training programs. Moderated mediation was used to test the hypotheses. Findings: Motivation to transfer (MTT) mediated the relationship between PS and perceived training transfer. When more coworkers participated in the training, PS had a stronger influence on trainee MTT. Practical implications: Organizations should consider training coworker cohorts at the same time to influence MTT and training transfer. Generally, whole-team training programs could be used to boost training transfer outcomes, although it could potentially have a negative impact on transfer if PS is low. Originality/value: To the best of the authors' knowledge, this was the first study to demonstrate that the number of coworkers participating in training can moderate the effect of PS on MTT and training transfer.