Traumatic brain injury (TBI) has turned into a major health and socioeconomic problem affecting young people and military personnel. Numerous TBI patients experienced the sequela of brain injury called cognitive impairment, which reduced functions in attention, working memory, motivation, and execution. In recent years, transcranial near-infrared laser therapy (tNiRLT) as a possible therapy has been gradually applied in treating cognitive impairment post-TBI. In the present review, the biological mechanisms of transcranial tNiRLT for TBI are synthesized mainly based on the photonic impact of chronic mild TBI. Various exciting molecular events possibly occur during the procedure, such as stimulation of ATP production, regional cerebral blood flow, acupoint, neurogenesis and synaptogenesis, as well as a reduction in anti-inflammatory effect. Some animal experiments and clinical studies of tNiRLT for TBI are outlined. Several labs have displayed that tNiRLT is effective not only in improving neurological functions but also in increasing memory and learning capacity in rodent animals’ model of TBI. In a 2 patients case report and a 11-case series, cognitive functions were ameliorated. Efficacy on cognitive and emotional effects was also observed in a double-blind, controlled clinical study. Several Randomized, parallel, double blind, sham-controlled trials are underway, aiming to evaluate the efficacy of tLED on cognitive functions and neuropsychiatric status in participants post-TBI. Therefore, tNiRLT is a promising method applied to cognitive impairment following TBI.