The importance of individual and group resources for predicting performance is a well-known debate in the literature. This paper presents one of the first attempts to examine the concurrent and relative effects of internal (self) and external (collective) efficacies on performance. We argue that one of the underlying mechanisms that affect the importance of these resources depends on the individual’s internal working model of attachment. Study 1 examined the moderating role of employees' attachment orientations in the relative importance they ascribe to self and collective efficacies for predicting performance. Study 2 examined the moderating role of managers' attachment orientations in the importance they attribute to employees' self and collective efficacies in predicting their subordinates' performance. Two samples of employees (N = 143) and managers (N = 132) in high-tech industries participated in these studies. Findings indicate that both employees and managers evaluated self-efficacy as a better predictor of performance than collective efficacy. Moreover, the analysis of both employees' and managers' attachment orientations illuminates how self vs. collective efficacy contribute to performance predictions. Findings also underscore the contribution of attachment theory to performance predictions in the workplace.