Drug-induced liver injury (DILI) is an adverse reaction to drugs or other xenobiotics that occurs either as a predictable event when the subject is exposed to toxic doses of some compounds (acetaminophen overdose) or in an unpredictable way with many drugs in common use. Drugs can be harmful to the liver in a susceptible subject on the background of genetic and environmental factors. This accounts for modifications in the hepatic metabolism and excretion of the agent leading to cellular stress, direct cell death, activation of an adaptive immune response and a failure to adapt with progression to overt liver injury. Idiosyncratic DILI is a relative rare liver disorder but can be severe and even fatal, presenting with a variety of phenotypes, which mimic almost every other liver disease. Diagnosis of DILI relies on the exclusion of other etiologies of liver disease as specific biomarkers are still lacking. Clinical scales such as CIOMS/RUCAM can support the diagnostic process but need a refinement. A number of clinical variables, validated in prospective cohorts, can be used to predict a more severe DILI outcome. Although no pharmacological therapy has yet been adequately tested in randomized clinical trials, corticosteroids can be useful, particularly in the emergent form of DILI related to immune checkpoint inhibitors.