Adopting a two-wave mediational design, the study investigated: a) self-efficacy as an antecedent of job crafting; b) the impact of crafting behaviors on job performance; c) the mediating role of job crafting in the relationship between efficacy beliefs and job performance. White-collars (N = 465) participated in the study, filling an online questionnaire in two succeeding years, then matched with performance ratings provided by the Human Resource Department at the end of each year. The longitudinal structural equation model revealed that efficacy beliefs positively related to job crafting, which predicted performance evaluations. More importantly, crafting behaviors fully mediated the association between self-efficacy and performance. Additionally, some evidence for a reciprocal causation between self-efficacy and job crating was provided.