Vitamin and fatty acid deficiency in children diagnosed with autism has been linked to the etiology and course of the disease but the results have been inconsistent. In our work, we present a narrative review, which includes 20 observational studies that provide data on the blood levels of vitamin D, folate, or fatty acids of children diagnosed with ASD (Autism Spectrum Disorder--AG group), and of a control group (children without this disorder--CG group). The main characteristics and results are presented in a summary table. Of the 20 above-mentioned studies, a meta-analysis of vitamin D and folate levels was carried out in 14 of them, with a total of 2269 children (AG = 1159, CG = 1110). Vitamin D levels were lower in AG compared to CG: SMD, 95% CI = - 0.83 [- 1.15, - 0.50]. In terms of folate levels, a total of 299 children (AG = 148, CG = 151) were analyzed, finding no significant differences with the control group: SMD, 95% CI = - 0.16 [- 0.63, 0.32]. Only one study that provided data on fatty acids in children with ASD was included in the review although it was not possible to include it in the meta-analysis. We conclude that the nutritional status (vitamin and fatty acid levels) of patients diagnosed with ASD should be taken into account, as correct adjustment of these levels--may produce an improvement in the course of the disease and could also reduce the risk of its development.