Introduction: Autism Spectrum Disorder (ASD) is a lifelong neurodevelopmental disorder that increased in prevalence in the last few decades, most notably among older adults. The gap in knowledge of aging processes, among individuals with ASD, and the increasing prevalence of Parkinsonism diagnosis in this population, revealed a need for research efforts. Nevertheless, differences in the group and age-related differences in cortical thickness in brain regions associated with motor control remain relatively unexplored. Objective: In this study, we analyzed cross-sectional data to investigate group differences and age-related differences in cortical thickness of the left hemisphere (lh) and right hemisphere (rh) of the precentral gyrus and paracentral lobule, in adults with ASD vs. NT adults. Knowing that individuals with ASD present greater group and age-related motor impairments than NT individuals, we tested the following hypothesis: adults with ASD will demonstrate reduced cortical thickness and greater relationships between increasing age and decreasing cortical thickness in the precentral gyrus and paracentral lobule than the NT participants. Methods: Group and age-related differences in cortical thickness were analyzed in our cohort of 191 participants with (N=105; ages 18-71) and without ASD (N=86 ages 18-70). T1-weighted MRI images were collected from each participant and were analyzed using FreeSurfer to obtain cortical thickness measurements from the motor regions of interest. Using SPSS (IBM SPSS Statistics for macOs, Version 28.0.1.1) univariate general linear models were used to test the between-subject effects of group, age, and group by age interaction, with sex as a covariate. Results: A statistically significant effect of the diagnosis group on cortical thickness was only observed in the lh precentral gyrus, with the ASD group showing a thinner cortex than the NT group. A statistically significant group-by-age interaction was present in the cortical thickness of the lh precentral gyrus, the rh precentral gyrus, and the lh paracentral lobule. For each interaction, the relationship between age and cortical thickness had a steeper negative slope in the ASD group compared to the NT group. Discussion: Consistent with our hypothesis, findings indicate ASD affects cortical thickness and may be linked to greater age-related reduced cortical thickness, of the studied motor areas, in adults with ASD compared to NT adults. Future research is warranted to investigate the relationship between cortical thickness in motor regions and the severity of motor impairments in the ASD population. Further longitudinal investigations of the age-related changes (trajectories) in cortical thickness, specific to motor regions, in individuals with ASD, are also necessary.