Autism spectrum disorder (ASD) is a clinically heterogeneous neurodevelopmental 
disorder that is caused by gene-environment interactions. To improve its 
diagnosis and treatment, numerous efforts have been undertaken to identify 
reliable biomarkers for autism. None of them have delivered the holy grail that 
represents a reproducible, quantifiable, and sensitive biomarker. Though blood 
platelets are mainly known to prevent bleeding, they also play pivotal roles in 
cancer, inflammation, and neurological disorders. Platelets could serve as a 
peripheral biomarker or cellular model for autism as they share common 
biological and molecular characteristics with neurons. In particular, 
platelet-dense granules contain neurotransmitters such as serotonin and 
gamma-aminobutyric acid. Molecular players controlling granule formation and 
secretion are similarly regulated in platelets and neurons. The major platelet 
integrin receptor αIIbβ3 has recently been linked to ASD as a regulator of 
serotonin transport. Though many studies revealed associations between platelet 
markers and ASD, there is an important knowledge gap in linking these markers 
with autism and explaining the altered platelet phenotypes detected in autism 
patients. The present review enumerates studies of different biomarkers detected 
in ASD using platelets and highlights the future needs to bring this research to 
the next level and advance our understanding of this complex disorder.