Recently, theory and research have supported psychological capital (PsyCap) as an emerging core construct linked to positive outcomes at the individual and organizational level. However, to date, little attention has been given to PsyCap development through training interventions; nor have there been attempts to determine empirically if such PsyCap development has a causal impact on participants' performance. To fill these gaps we first conducted a pilot test of the PsyCap intervention (PCI) model with a randomized control group design. Next, we conducted a follow-up study with a cross section of practicing managers to determine if following the training guidelines of the PCI caused the participants' performance to improve. Results provide beginning empirical evidence that short training interventions such as PCI not only may be used to develop participants' psychological capital, but can also lead to an improvement in their on-the-job performance. The implications these findings have for human resource development and performance management conclude the article. (Contains 1 figure and 4 tables.)