--- - |2+ Abstract Objective Across all subfields of psychology, it is common practice to use different indicators of allegedly the same personality constructs, resting upon the (often implicit) assumption that the indicators measure equivalent constructs. However, there is a lack of approaches allowing for a strict and comprehensive test of the equivalence assumption. We propose investigating nomological consistency to test the equivalence assumption across inventories allegedly measuring the same set of constructs. Nomological consistency refers to the degree to which different indicators of constructs in a theoretical or structural model (such as the Big Five) show similar (non‐)associations with a set of external criteria, thus testing the consistency of the nomological net spanned by different indicators. Method In a large‐scale study based on a convenience sample (N = 2,846; 64.9% female), we provide an empirical demonstration of nomological consistency across three commonly used Big Five inventories by comparing the pattern of associations of the Big Five constructs across inventories with five external criteria using a multifaceted analytic approach. Results Although results showed some level of consistency across the Big Five inventories under scrutiny, there was also a relevant extent of nomological inconsistency. Conclusions Testing nomological consistency allows for a more conclusive judgment on the equivalence of different indicators across inventories. - Journal of Personality, EarlyView.