The purpose of this study is to explore the relationship among skill variety, autonomy, and job involvement with the mediating effect of informal learning in the South Korean business context. This study adopts a cross-sectional survey-based research design, drawing on the responses of 226 South Korean trainers to a survey regarding their facilitation experiences. Structural equation modeling is used in order to examine the influential relationship among the research variables. The results suggest that trainers exhibit higher levels of job involvement when they possess significant skill variety and high levels of autonomy and informal learning. Moreover, informal learning is shown to mediate the relationship between the job characteristics and job involvement. Recent changes in the knowledge economy have required professional trainers to expand their capabilities to lead organizations in the execution of business strategies. This study highlights the importance of informal learning to the trainers' professional and career advancement.