Drawing upon human capital theory and attachment theory, this study develops a research model that examines how on-the-job training (OJT) effectiveness and work engagement play key mediating roles in the development of job performance. In the proposed model, job performance is indirectly influenced by cultural learning, professional learning, and mentorship learning via the full mediation of OJT effectiveness. At the same time, job performance is also influenced by social interaction, leader support, and self-efficacy via the full mediation of work engagement. Employees’ sense of responsibility and leader support both play moderating roles in the research model. The hypotheses were empirically tested using both primary data from a survey on new employees of a leading financial holding company in Taiwan’s banking industry and secondary data from the company’s database of human resource management (HRM) regarding the training and education of the new employees. JEL Classification: D23, M53, O15