The three-way interaction effect of (broad-based) employee share ownership (ESO), training, and early promotion policy on labor productivity was examined in a longitudinal sample of 614 organizations (1,605 organization-year data points) in Korea. The ESO–productivity relationship was positive only when the investment in training was high and the opportunity for early promotion was present. However, we found no evidence for the two-way interaction effects of ESO and training and ESO and early promotion policy on labor productivity. The results are in alignment with the emergent view that the productivity benefits of ESO can be better realized when ESO coexists with a bundle of complementary human resource management (HRM) practices. Thus, this study meaningfully extends the contingency perspective and related studies in the ESO literature, which tend to examine the productivity effect of ESO in isolation or in conjunction with a single HRM practice.