Background: In Parkinson’s disease, deep brain stimulation (DBS) of the subthalamic nucleus (STN) or globus pallidus internus (GPi) produces comparable motor benefits. Although both increases the risk of cognition and verbal fluency (VF) decline, the risk is greater following STN-DBS. The consequences of stimulating these different sites on brain network activity is unknown. We use functional magnetic resonance imaging (fMRI) during in vivo stimulation to investigate differences between STN-DBS and GPi-DBS and correlate with change in VF. Methods: Left-sided, stimulation-cycling block-design fMRI was acquired at 3-Tesla in 51 STN-DBS and 15 GPi-DBS following routine clinical programming. Blood oxygen level-dependent (BOLD) response to stimulation was compared between groups. Phonemic VF was assessed pre- and postoperatively. Results: Voxel-wise t-test between STN-DBS and GPi-DBS BOLD response maps revealed areas of significant difference (p<0.001) in the left frontal operculum and the left caudate head. Stimulation BOLD response appears to show slight inverse correlation with postoperative VF decline. The trend is reversed at the left frontal operculum in STN-DBS compared to GPi-DBS. Conclusions: Decline in VF in PD-DBS seems associated with the stimulation BOLD response at the left frontal operculum and the left caudate head. The effect differs depending on stimulation site, suggesting differing effects on brain network activity.