In order to investigate which instruments are most utilized when measuring perceived and experienced mental illness stigma (MIS) in adults, and some of the variables that may moderate or interfere in measured outcomes, 101 published empirical and peer-reviewed studies were systematically extracted from electronic databases (PubMed, Scopus, EBSCO, Web of Science, and PsycINFO). The results revealed that MIS is commonly evaluated by five scales. When considering the most tested and reported associative effects, age, and symptoms' severity were identified as potentially intervening variables. Other variables, such as sex, diagnostic, and treatment regimen (inpatient/outpatient) were evaluated by a few studies and presented inconsistent results. These findings suggest that future studies should use well-established instruments in the literature to assess MIS, as well as to aim for the cross-cultural adaptation of instruments that evaluate MIS since no instruments presented in this review are validated to the Brazilian population.