PurposeDrawing on the conservation of resources theory, this study examines how proactive skill development (PSD) influences job performance and mediating and moderating mechanisms underlying the above relationship.Design/methodology/approachData were collected from a sample of 261 full-time workers in three waves, spaced by a six-week interval (Time 1, N = 360; Time 2, N = 320; Time 3, N = 261).FindingsThe results confirmed that career stress mediated the relationship between PSD and job performance. Additionally, high career decidedness strengthened this negative relationship between stress and performance. Furthermore, career decidedness significantly moderated the indirect PSD–performance relationship via career stress, accentuating the indirect effect when decidedness is higher.Originality/valueThis study sheds light on the important role of proactive skills development in influencing job performance and what factors can affect this relationship. It offers practical implications by highlighting how targeted training can boost employees' proactivity and performance.