Bipolar disorder (BD) is a debilitating psychiatric disorder characterized by mood disturbances and executive function deficits. Impairments in executive function, including impulsivity, significantly impact the daily lives of individuals with BD. Transcranial photobiomodulation (t-PBM) with near-infrared light offers a promising noninvasive neurostimulation approach to improve cognitive function. The Transcranial Photobiomodulation for Executive Function in Bipolar Disorder (TPEB) study aims to explore the potential of t-PBM in individuals with BD and executive function impairments. This study will include 20 adults with BD who will each receive one sham and one t-PBM session on the first day of stimulation (treatment day 1), followed by one daily t-PBM stimulation session for four days (treatment days 2 to 5). Cerebral blood flow changes will be evaluated using functional magnetic resonance imaging. Impulsivity, decision-making, and reward responsiveness will be assessed using the Barratt Impulsiveness Scale, the Iowa Gambling Task, and a gambling task that evaluates reward. The outcomes involve examining changes in cerebral blood flow, improvements in decision-making, and reductions in impulsivity and manic symptoms. The TPEB study aims to provide valuable insights into the potential of t-PBM as a therapeutic intervention to enhance executive function in BD.