SIGNIFICANCE: The current neuromodulation treatment for post-stroke cognitive impairment (PSCI) is formulated based on interhemispheric inhibition, which is particularly relevant in the context of motor disorders after stroke. However, the pathological mechanism of PSCI remains unclear, which is completely different from motor disorders. Therefore, exploring the pathological brain characteristics of PSCI can provide a reliable theoretical basis for effective neuromodulation treatment for it. AIM: We explored different functional connectivity (FC) manifestations of PSCI with or without aphasia via functional near-infrared spectroscopy (fNIRS) to provide a pathological basis for the neuromodulation strategy. APPROACH: We collected cognitive performance and fNIRS data from patients with PSCI without aphasia (PSCI group, RESULTS: The overall FC in the PSCI group was lower than that in the SC or HC group, and the FCs of the right hemisphere, the right default mode network (DMN), and the right central executive network (CEN) of PSCI patients were significantly lower than those of the left ones. In the PSA group, the FCs of the DMN and CEN were not lower than those in the SC and HC groups, and the FC of the left hemisphere was significantly greater than that of the right hemisphere. In addition, the FC of PSCI patients with right lesions was weaker than that of left lesions, which was closely correlated with the cognitive scale. CONCLUSIONS: Unlike the left hemisphere activation strategy commonly used previously, our results suggest that the important role of the right hemisphere may be overlooked in PSCI patients with or without aphasia. Future treatment options and studies could consider focusing on the right hemisphere or bilateral hemispheres.