Anti-drug antibodies (ADAbs) develop in up to a third of patients treated with biologic agents, with such immunogenicity being one of the main reasons for the loss of efficacy observed in an important proportion of patients treated with such agents. The appearance of ADAbs has consequences in terms of efficacy and tolerance of the biodrug: the development of ADAbs is associated with a poorer clinical response and with an increased risk of adverse effects. Formation of ADAbs has been observed with all biologic DMARDs, but anti-TNF agent mAbs appear to be the largest contributors, independent of humanization of the antibody. ADAb identification is technically difficult and not standardized, partly explaining important variations between published studies. A variety of factors can influence the risk of ADAb appearance, some of which are linked to the treatment strategy, such as the combination with synthetic DMARDs or the rhythm of administration of the biodrug, whereas other factors are dependent on the patient, such as the level of inflammation at onset or body weight. The detection of these antibodies and/or the dosage of the biologic agent itself could have consequences for the bedside practice of clinicians and should be well understood. This review of the literature proposes an overview of the data published on the subject to help clinicians manage the biodrugs according to these new concepts.