Introduction: Although the burden of adverse drug reactions (ADRs) has a significant impact on patients’ quality of life, thorough knowledge about patients’ perspectives on the burden of ADRs attributed to biologics is lacking. Objectives: This study was conducted to gain insight into the patient burden of ADRs experienced with biologic use. Methods: The Dutch Biologic Monitor is a prospective, multicentre, event monitoring cohort system including information collected by web-based questionnaires from patients using biologics, mainly for immune-mediated inflammatory diseases (IMIDs). Patients were asked to complete bimonthly questionnaires on biologics used, indication for the biologic, experienced ADRs, consequences of ADRs and burden on a five-point Likert-type scale, ranging from 1 (no burden) to 5 (very high burden). We assessed potential factors associated with patient-reported burden of ADRs. Results: A total of 1355 patients completed 6293 questionnaires between 1 January 2017 and 1 May 2019. Almost half of the patients (665 patients, 49%), 69% with rheumatic diseases and 31% with other diseases, collectively reported 1720 unique ADRs. Infections and musculoskeletal complaints were the most burdensome ADRs and injection-site reactions were the least burdensome. ADRs leading to healthcare professional contact were more burdensome than ADRs without healthcare professional contact. Smoking, respiratory and psychiatric comorbidities were associated with higher burden of ADRs. Crohn’s disease, use of adalimumab and use of sulfasalazine as combination therapy were associated with lower burden of ADRs. Conclusions: The patient perspective gives important insights into the burden of ADRs experienced with biologics. This information could be used by healthcare professionals to optimise treatment with biologics.