Purpose - The purpose of this paper is to examine the effects of job demands, job resources and personal resources on work engagement using the job demands–resources (JD–R) model. Design/methodology/approach - The study utilized a longitudinal research design in a sample of Thai employees ( Findings - The results supported the negative relationship between role ambiguity and work engagement. In addition, the findings suggested self-efficacy as a moderator in reducing the effect of increasing workload on work engagement. Research limitations/implications - The results of this study will be helpful for managers in designing appropriate human resources policies and practices; in recruiting, selecting and developing engaged employees; and in ensuring workplace well-being. Originality/value - This is the first notable study establishing the applicability of the antecedents of work engagement in the JD–R model in a Thai work setting.