This study describes the adverse drug reactions (ADRs) and their incidence in patients with rheumatoid arthritis who were treated in the Colombian health system. A retrospective cohort study was conducted using information from all patients who were diagnosed with rheumatoid arthritis and attended specialized health care centers in the cities of Bogotá, Cali, Manizales, Medellin, and Pereira between 1 December 2009 and 30 August 2013. The ADRs were obtained from medical records and the pharmacovigilance system registry and sorted by frequency and affected tissue according to World Health Organization Adverse Reaction Terminology (WHO-ART). A total of 949 reports of ADRs were obtained from 419 patients (32.8 ADRs per 100 patient-years); these patients were from a cohort of 1,364 patients being treated for rheumatoid arthritis and followed up for an average of 23.8 months (± 12.9). The cohort was mostly female (366, 87.4%) and had a mean age of 52.7 years (± 13.1). The highest numbers of ADRs were reported following the use of tocilizumab, rituximab, and infliximab (28.8, 23.1, and 13.3 reports per 100 patient-years respectively). The most frequently reported ADRs were elevated transaminase levels and dyspepsia. Overall, 87.7% of ADRs were classified as type A, 36.6% as mild, 40.7% as moderate, and 22.7% as severe. As a result, 73.2% of patients who experienced an ADR stopped taking their drugs. The occurrence of ADRs in patients treated for rheumatoid arthritis is common, especially in those associated with the use of biotechnologically produced anti-rheumatic drugs. This outcome should be studied in future research and monitoring is needed to reduce the risks in these patients.