This study investigates the role of irrational beliefs at work in two Italian samples. The first aim was to evaluate the psychometric properties of an Italian adaptation of the Work-related Irrational Beliefs Questionnaire (WIB-Q; Van Wijhe, Peeters, & Schaufeli, 2013). The four-factor structure (i.e., performance demands, coworkers’ approval, failure, and control) was confirmed and the WIB-Q showed satisfactory convergent, discriminant, and criterion-related validity. The second aim of this study was to test a theoretical model in which irrational beliefs at work mediate the association between self-oriented perfectionism (SOP) and socially prescribed perfectionism (SPP) on the one hand and workaholism on the other. Failure mediated the association between SOP/SPP and workaholism, whereas the mediating effect of performance demands was marginally significant. Overall, the results of this study suggest that interventions aimed at preventing workaholism should target perfectionists’ work-related irrational beliefs related to failure and performance demands. (read more).