Cytokines and growth factors are proteins that mediate the activity and survival of many cells in human body. One of the ways in which this mediation takes place is via JAK / STAT signaling path. Cytokines bind to their receptors on the cell surface and, by conformational change, trigger a signaling cascade which is continued by phosphorylation. Janus (JAK) kinases are intracellular tyrosine kinases which are associated with cytokine receptors. Kinases are responsible for the consequential phosphorylation of downstream molecules. Given the wide range of effects that JAK / STAT pathway has on immune and blood cells, the fact that Janus kinases have become an attractive therapeutic target in the treatment of autoimmune and hematological diseases is not surprising. A number of downstream targets affected by Janus kinase inhibition also has one disadvantage which is the safety profile of these potent drugs. The aim of this study was to analyze the side effects of JAK inhibitors reported to the Agency for Medicinal Products and Medical Devices of Croatia in the period from 1 January 2013 to 11 July 2021. Also, another intention was to increase awareness of the safe profile of these drugs and risk minimization measures. Received reports of suspected adverse reactions were analyzed in relation to the total number of received reports in a given period, reporter qualification, age and sex of the patient, seriousness of reactions, seriousness criteria, most commonly reported reactions, reported reactions by MEdDRA organic classification (Medical Dictionary for Regulatory Affairs) and most commonly applied medicines.The obtained results and knowledge about the safe profile of JAK inhibitors and risk minimization measures enable additional education of healthcare professionals on effective prevention, detection and treatment of possible side effects, all with the purpose of improving the quality of life of patients.