Gastrointestinal (GI) dysfunction in ASD may be due to the disturbance of the gut microbiota composition and metabolism. The object of this study to find out the effect of dietary intervention with probiotic and pumpkin seeds oil (PSO) on the severity of GI symptoms among autistic children. An intervention clinical trial was conducted on ASD children divided into three groups: PSO supplemented with PSO (1gm per day); probiotic group (PrG) supplemented with 1gm tablet per day; and combined group (PPG) administered both supplements interval for eight weeks. The results stated that the majority of autistic children were graded at a moderate level of the 6-GSI index, after the dietary intervention the symptoms improved and the children were classified into a less severe stage. The presence of dysbiotic bacteria as Firmicutes Clostridium was significantly diminished after intervention with probiotic, also faecal pH begins to neutralise to alkalinity in PrG and PPG. Also, faecal secretary IgA (SIgA) was reduced significantly (P≤0.001) by 12.72, 13.14, and 16.22 % for POG, PrG, and PPG respectively. Mucus secretion reduced significantly (P≤0.05) to fewer quantities by (19.2 % vs 50%), (23.5 % vs 58.8 %) in PPG and PrG, respectively. The study concluded that dietary intervention with probiotic and PSO could be used as a therapeutic plan in changing the composition of intestinal microbiota, decrease inflammation and return epithelial barrier function to ameliorate the severity of gastrointestinal symptoms of ASD children.