Autism spectrum disorder (ASD) represents a complex neurodevelopmental disorder, being associated with various metabolic abnormalities. Micronutrients, including selenium (Se), are frequently used for ASD management. However, their efficiency remains unclear. Moreover, data on the role of Se metabolism in ASD are insufficient and contradictory. Therefore, the objective of this chapter is to review the existing data on Se status of children with ASD. Current data demonstrate that Se intake varies in children with ASD from low to high values in comparison to the daily recommendations. Similarly, data on Se status in ASD are also contradictory. Of 16 studies reviewed, eight indicate decreased Se levels in samples from autistic children, whereas six demonstrate opposite changes. Correspondingly, two recent meta-analyses failed to reveal any significant association between Se status and ASD. The activity of GPX in children with ASD is also highly variable from study to study. The observed difference in Se level in ASD patients may be related to different substrates used, as well as to specific features of the studied populations. However, the existing studies indicate involvement of Se imbalance in metabolic/psychometabolic disturbances in ASD. The mechanisms of a proposed Se neuroprotective effect in ASD may involve inhibition of oxidative stress, neuroinflammation, and microglia activation. In addition, synaptic dysfunction and gut-brain axis disturbances might be modified. However, further studies are required to highlight the mechanisms of the potential neuroprotective effects of Se in ASD as well as its efficiency in clinical trials. © Springer International Publishing AG, part of Springer Nature 2018.