Introduction: The aim of this study is to determine whether there is a difference in serum Zonulin, Occludin, Claudin-5, Junctional Adhesion Molecule-A (JAM-A), Tricellulin levels between individuals diagnosed with Autism Spectrum Disorder (ASD) and healthy controls. Method: A total of 40 children with ASD and 40 controls aged 2-12 years were enrolled in this study. Serum levels of biochemical variables were determined using commercial enzyme-linked immunosorbent assay kits. Childhood Autism Rating Scale, Autism Behavior Checklist and Aberrant Behavior Checklist were applied to determine the severity of autistic symptoms. Results: Serum Zonulin, Occludin, Claudin-5, Tricellulin and JAM-A levels did not differ between the study and control groups. There was no relationship between the severity of ASD symptoms and biochemical parameters. Discussion: Although the findings of the study suggest that the permeability of the Blood Brain Barrier (BBB) is not effective in the etiology of ASD, there is a need for new studies addressing the limitations of our study in a larger and heterogeneous sample in order to generalize the findings.