Nonalcoholic fatty liver disease (NAFLD) is a multifaceted disorder that ranges from simple fatty liver to nonalcoholic steatohepatitis (NASH) with or without fibrosis, which may evolve toward cirrhosis and hepatocellular carcinoma. It is currently considered a “global” and “epidemic” disease, whose prevalence is progressively increasing even in pediatric age. The incidence of NAFLD is very high in overweight/obese children, and a greater risk of disease progression is associated with severe obesity, highlighting the role of nutrition. To date, for NAFLD, there are few guidelines for diagnostic and follow-up methods, and scarce validated protocols for treatment. The initial indications consist of gradual weight loss and regular exercise, but in children, the difficulty of adhering to long-term behavioral changes makes this approach limited. The purpose of this narrative review is to examine the mechanism underlying the pathogenic mechanisms that lead to NAFLD in children, with a major focus on the role of nutrition. Because this is particularly relevant in light of the absence of pharmacological treatments suitable for children, we also overview clinical studies on the potential effects of nutritional supplementations, including vitamins, docosahexaenoic acid, and probiotics.in children. To this aim, updated search was conducted on PubMed and clinicaltrials.gov databases. Future research should consider additional clinical studies in pediatric NAFLD patients to validate the benefits of dietary supplements and to define the appropriate dosage and duration for intervention. Furthermore, experimental studies with -omics approaches could be helpful to deepen the related mechanisms and to search for a possible optimal supplement combination against NAFLD in children.