Job crafting is beneficial for employees and organizations. To better predict these behaviors, we introduce the concept of job crafting self-efficacy (JCSE) and define it as an individual's beliefs about their capability to modify the demands and resources of their job to better fit their needs. This article describes the development and validation of a scale to measure JCSE. We conducted a qualitative study to design and four quantitative studies to test the psychometric properties of this scale among Polish and American employees in both paper-and-pencil and online versions. Three independent (N1 = 364; N2 = 432; N3 = 403) confirmatory factor analyses demonstrated a good fit to a 3-factor solution comprising JCSE beliefs about increasing (a) structural job resources, (b) social job resources, and (c) challenging job demands. The 9-item JCSE Scale had good internal consistency, high time stability, and good validity. It correlated positively with general self-efficacy. JCSE explained unique variance in job crafting behaviors over and above general self-efficacy, and was more important in predicting job crafting than contextual factors. We demonstrate the role of social cognitions in shaping job redesign behaviors and provide a useful tool to evaluate the effectiveness of interventions dedicated to empowering JCSE.