This study investigates the effects of core self-evaluations, job autonomy, and intrinsic motivation on employees' perceptions of their in-role job performance, based on a cross-sectional survey of 283 employees in a Fortune Global 100 company in Korea. The results suggest that employees perceived higher in-role job performance when they had higher core self-evaluations and intrinsic motivation. Intrinsic motivation partially mediated the relationship between core self-evaluations and job performance, and it also fully mediated the relationship from job autonomy to job performance. Thus, to increase motivation and job performance, managers and HRD professionals need to create an integrated strategy incorporating enhancement of selection methods, elements of job redesign, and interpersonal developmental practices such as coaching and mentoring. (Contains 2 tables and 3 figures.)