Despite the effectiveness of biologics approved for the treatment of rheumatoid arthritis, they have been associated with serious adverse events (AEs). Biologics are used under close supervision of health care professionals. In Portugal, they are legally required to report AEs occurring during the treatment. This study aims at investigating post-marketing safety monitoring data of biologics in Portugal by comparing the frequency of spontaneously reported adverse events between 2009 and 2011 with the frequency of such events in the summary of the product characteristics of each biologic. Sales data for biologics were obtained from IMS Health and converted into defined daily doses/1,000 inhabitants/day in order to estimate a proportion of the population treated. The frequency of AEs was estimated as the percentage of patients in which an AE may have occurred. The use of each biologic was estimated for adalimumab at 1,439 patients/year, etanercept 1,944 patients/year, and infliximab 3,211 patients/year. A total of 992 AEs were reported: 207 for adalimumab, 199 for etanercept, and 586 for infliximab. Of the 515 different spontaneously reported AEs, 194 were included for comparisons with the SPCs. Of those, 31 (16 %) were similarly frequent, and 163 (84.0 %) occurred less frequently compared with SPCs' data. These results suggest an insufficient post-marketing safety monitoring of biologics in Portugal.