Background: Neurofilaments are intermediary filaments associated with neurodegenerative processes. Thrombospondin-1 (TSP-1) is a biological marker playing a role in synaptogenesis. This study aimed to investigate serum neurofilament light chain (NFL), and TSP1 levels of patients with autism spectrum disorder (ASD) compared to typically developing (TD) children. Methods: Forty-three patients with ASD and forty-five TD children were included. Serum biomarker levels were measured using the sandwich ELISA technique. The Childhood Autism Rating Scale (CARS) was implemented to measure the severity of ASD. Results: NFL and TSP1 levels did not differ between study groups (For NFL, ASD = 47.8 ± 11.4 vs. TD = 48.2 ± 15.3 pg/mL, p = 0.785; for TSP1, ASD = 224.4 ± 53.7 vs. TD = 224.7 ± 69.0 ng/mL, p = 0.828). Stereotyped behavior and sensory sensitivity domain of the CARS scale was negatively correlated with serum TSP-1 (r = -0.390, p = 0.010) and NFL (r = -0.377, p = 0.013) levels. Age was also positively correlated with NFL levels (r = 0.332, p = 0.030) in the ASD groups but not in the TD group. Discussion: Our results did not support the neurodegenerative process of ASD. Future studies are needed to investigate neuroprogression in a longitudinal follow-up. Keywords: Neurofilament light chain; autism; neurodegeneration; thrombospondin.