Problematic smartphone use (PSU) is common among young people and linked to poor academic performance. However, how PSU affects learning processes remains unclear. This study investigated the influence of auditory cue stimulation during a reading task on the mental workload and prefrontal brain activity of young individuals with PSU. Sixteen university students with PSU and 14 healthy controls (HC) performed a silent reading task, during which fake notification sounds were introduced. Their mental workload was assessed using the NASA Task Load Index (NASA-TLX), and prefrontal brain activity was measured using functional near-infrared spectroscopy (fNIRS). The results of the NASA-TLX suggest that the PSU group experienced greater frustration than the HC group. The fNIRS results showed that in the right medial prefrontal region of the HC group, O2Hb levels increased following cue stimulation, whereas no change was observed in the PSU group. Moreover, in the HC group, HHb levels in the left lateral prefrontal region decreased after cue stimulation. The findings of the present study demonstrate that university students with PSU experience frustration and exhibit deactivation in the prefrontal regions associated with the executive control network during silent reading in realistic learning situations.