Haff disease is a condition associated with the consumption of fish of different species reported in different parts of the world. Many etiological hypotheses for Haff disease have been proposed. However, it is still not possible to precisely state the cause. Currently, the most accepted hypothesis is that the disease is caused by some toxin. The most common clinical manifestation is myalgia, present in almost 100% of cases. Gastrointestinal symptoms, such as nausea, vomiting, and diarrhea, may occur frequently, as well as abdominal pain, headache, and dizziness. The presence of dark urine, which popularly has become synonymous with Haff disease (“black urine disease”), is not present in all cases. Laboratory tests may evidence an increase in serum levels of creatine phosphokinase (five times the normal value). As in other situations of toxic rhabdomyolysis, the main and most common kidney dysfunction observed in Haff disease is acute kidney injury (AKI). The progression to severe AKI and the need for renal replacement therapy in Haff disease are quite variable. There is no specific therapy for Haff disease, so once the diagnosis has been suspected based on a typical history and after a thorough anamnesis, complementary tests should be performed for early diagnosis of rhabdomyolysis and staging.