Blood homocysteine appears to be increased in Parkinson's disease (PD) and may play a role in the development and progression of this disorder. However, the specific contribution of abnormal homocysteine levels to cortical degeneration in PD remains elusive. To characterize the cortical structural correlates of homocysteine levels in PD. From the COPPADIS cohort, we identified a subset of PD patients and healthy controls (HC) with available homocysteine and imaging data. Surface-based vertex-wise multiple regression analyses were performed to investigate the cortical macrostructural (cortical thinning) and microstructural (increased intracortical diffusivity) correlates of homocysteine levels in this sample. A total of 137 PD patients and 43 HC were included. Homocysteine levels were increased in the PD group (t = −2.2, p = 0.03), correlating in turn with cognitive performance (r = −0.2, p = 0.03). Homocysteine in PD was also associated with frontal cortical thinning and, in a subset of patients with available DTI data, with microstructural damage in frontal and posterior-cortical regions (p < 0.05 Monte-Carlo corrected). Homocysteine in PD appears to be associated with cognitive performance and structural damage in the cerebral cortex. These findings not only reinforce the presence and importance of cortical degeneration in PD, but also suggest that homocysteine plays a role among the multiple pathological processes thought to be involved in its development. •Parkinson's disease (PD) patients appear to show increased homocysteine levels.•Homocysteine correlated in turn with cognitive performance in our PD sample.•Homocysteine was also associated with cortical macro- and microstructural alterations.•This metabolic marker may play a role in cortical degeneration in the PD population.