The objective of the study was to investigate the potential of a specific carbohydrate diet and selected dietary supplements in reducing some autistic spectrum disorder (ASD) symptoms in children. This was a quantitative, non-blinded, non-randomised three-month pilot study of a dietary and nutritional intervention. The study participants were 17 children from Latvia and the United Kingdom with a diagnosis of ASD or autistic symptoms waiting to be diagnosed (intervention group n = 10, control group n = 7). The intervention group received a specific carbohydrate dietary plan — Specific Carbohydrate Diet / Gut and Psychology Syndrome diet (SCD/GAPS) — and a few dietary supplements (omega-3 essential fatty acids, ascorbyl-palmitate, probiotics, vitamin D, and vitamin C). Family compliance to the dietary guidelines was 40–80%. Autistic and digestive symptoms were evaluated by parents using validated questionnaires. By the end of the study, gastrointestinal symptoms decreased in both groups (