Objectives <p>To characterize the network topology and peak width of skeletonized mean diffusivity (PSMD) and their correlation with cognitive impairment in obstructive sleep apnea (OSA) patients and to assess whether such impairments are reversible after treatment.</p> Methods <p>Ninety-one OSA patients and 30 healthy controls (HCs) participated. Patients were classified into mild group (<i>n</i> = 37) and moderate–severe group (<i>n</i> = 54) based on apnea–hypopnea index. Cognitive performances, including execution, visual memory, attention, and psychomotor speed were assessed. Network topological properties and PSMD, derived from resting-state functional MRI and diffusion imaging, were compared and correlated with their cognitive performance. Alterations in network topology, PSMD, and cognitive performance after treatment were assessed in a subcohort of patients.</p> Results <p>OSA patients had worse performance in the digit symbol test and Stroop color–word test than HCs, whereas the performance of moderate–severe OSA patients decreased more significantly. Mild OSA patients had compromised degree centrality of cognitive control, while moderate–severe OSA patients had compromised topological properties involving cognitive control, default mode, limbic, and auditory network relative to HCs, and had higher PSMD than mild OSA patients and HCs. Aberrant PSMD and functional nodal network metrics closely correlated with cognitive decline in OSA patients. Notably, functional network topology and cognitive performance partially improved in patients after treatment.</p> Conclusions <p>Progressive compromise of the PSMD and functional network topology may underlie the cognitive deficits in attention and processing speed in OSA patients. The disruption of functional network topology and cognitive performance are partially reversible in OSA patients after treatment.</p>