Functional near-infrared spectroscopy monitoring during transcranial photobiomodulation sessions successfully identified which older adults would experience cognitive benefits from the 12-week light therapy intervention. Among 29 participants with cognitive decline, those showing specific hemodynamic responses during treatment had measurably better outcomes on cognitive assessments. This represents a significant advance in personalized neurostimulation approaches. Previous tPBM studies have shown mixed results, with response rates varying widely between individuals, making treatment selection largely guesswork. The integration of real-time brain monitoring with therapeutic light delivery addresses a critical limitation in the field—the inability to predict who will benefit from these interventions. For aging adults considering cognitive enhancement strategies, this technology could eventually enable clinicians to identify optimal candidates before committing to lengthy treatment protocols. The approach also opens possibilities for dose optimization based on individual neural responses. However, the study's modest sample size and single-center design limit immediate clinical application. Replication across diverse populations and validation against gold-standard cognitive measures will be essential before this predictive approach can guide treatment decisions in clinical practice.