Nonalcoholic fatty liver disease (NAFLD) has been found to be highly prevalent in psoriatic patients. Adult onset psoriasis could be divided into either early or late onset psoriasis. The associations between NAFLD and related metabolic comorbidities and age at onset of psoriasis have not yet been investigated. Our study was to evaluate the associations between prevalence of NAFLD and related metabolic conditions and early, late, and childhood onset psoriasis. A cross-sectional observational study was conducted on patients with moderate to severe plaque psoriasis. Data on clinical characteristics of NAFLD and related metabolic diseases (diabetes, hypertriglyceridemia, hyperuricemia, and metabolic syndrome) were collected. The prevalence of NAFLD in 439 patients (mean: 51±14 years, range: 18–85 years) was 55.8%. NAFLD was frequently identified in early onset patients (74.2%), and this diagnosis was particularly common in patients currently younger than 40 (85.3%). Diabetes was the least prevalent component of metabolic syndrome in early onset patients with metabolic syndrome but the most often found component in late onset ones. Patients with childhood onset psoriasis had the lowest frequencies of all metabolic comorbidities except hyperuricemia among the three groups. In the multivariate analyses, early onset was independently and positively associated with NAFLD, hypertriglyceridemia and hyperuricemia and independently and negatively associated with diabetes among early and late onset patients. The results suggested prevalence of NAFLD and related metabolic comorbidities was associated with age at onset of moderate to severe plaque psoriasis. Early onset of psoriasis was independently associated with greater odds of NAFLD, hypertriglyceridemia, hyperuricemia and smaller odds of diabetes compared to late onset. Early onset patients have metabolic syndrome mainly related to lipid disorders and abnormal glucose metabolism was not often involved.