Numerous epidemiology studies confirm the increasing prevalence of non-alcoholic fatty liver disease in severe psoriasis, with more than double the risk reported for patients without psoriasis (odds ratio [OR] 2.15). Liver disease is more severe in patients with psoriasis than in controls without psoriasis and is associated with the severity. Similarly, patients with fatty liver disease have more severe psoriasis. This harmful synergy has a common pathogenic origin, resulting from the frequent association between both diseases, insulin resistance and the metabolic syndrome. The disease manifests with a greater intensity when both conditions co-occur than when each manifests separately. Furthermore, psoriasis and fatty liver also have a common cytokine-mediated inflammatory background, which involves an imbalance between pro-inflammatory and anti-inflammatory cytokines. In fact, each disease plays a role in the course of the other. The dermatologist should usually detect liver disease after a specific assessment of patients who present with the metabolic syndrome. The hepatologist should be aware of the more severe condition of these patients. Various medications, such as acitretin, cyclosporine and methotrexate may prove harmful for patients with liver disease. Biologics have proven to be safe in patients with chronic liver disease. Hepatologists and dermatologists should work together to ensure the careful evaluation of the optimal therapy for each patient depending on the severity of both diseases, taking care to avoid, where possible, hepatotoxic drugs and select options that may even have a shared benefit for both diseases.