Therapeutic monoclonal antibodies (mAbs) including antibody fusion proteins and antibody conjugates present an innovative class of (bio-)pharmaceuticals with increasing clinical importance. MAbs were initially perceived as comparatively safe drugs. As more mAbs appear on the market, characteristics of their safety profiles become apparent, including immunogenicity, i.e. the potential induced formation of human anti-drug antibodies (HADAs) in patients. European Public Assessment Reports were reviewed to provide an overview about main safety concerns and the immunogenicity of mAbs in chronic inflammatory diseases and oncology/haematology, including strategies for their prevention and clinical management. In total, both mechanism-related and non-specific adverse drug reactions (ADRs) have been reported, with infectious complications and administration-related reactions observed across the majority of mAbs. Most ADRs were predictable and manageable, although some have emerged unexpectedly. Immunogenicity occurred with almost all mAbs, with widely differing extent. Adverse consequences of HADAs were only identified for few mAbs. In conclusion, mAbs are generally safe but as they may be associated with significant ADRs, the individual risks need to be weighed against the expected therapeutic benefit. As several of the recently introduced mAbs are directed against new targets, and considering the limited understanding of immunogenicity, special caution and patient monitoring is highly recommended.