Cognitive function is a crucial aspect of brain functioning, but it can be compromised in various neurological pathologies and diseases, resulting in cognitive deficits. Currently, effective treatments and rehabilitation measures for cognitive impairment patients remain limited. Light treatment, as a non-invasive physical therapy, has emerged as a promising approach and has garnered increasing attention. This article provides an overview of the clinical application status of light treatment in cognitive impairment associated with neurological and psychiatric disorders, with a specific focus on Alzheimer’s Disease (AD), mild cognitive impairment (MCI), post-traumatic cognitive impairment (PTCI), and cognitive impairments linked to schizophrenia (CIAS). The mechanisms of improving effects of light treatment on cognition are multifaceted, including the regulation of circadian rhythms, neuroprotection and repair, enhancement of blood circulation, modulation of neurotransmitters, anti-inflammatory effects, promotion of neuroplasticity, and reduction of oxidative stress. Light treatment is believed to influence brain electrical activity. The inconsistent finding on the effects of 40 Hz light stimulation on cognitive impairment associated with neurodegenerative diseases may be related to the inconsistency between the light treatment paradigm and the animal model. The organic or structural damage of neurons during the middle or late stages of the disease limits the preventive and ameliorative effects of light treatment. Additionally, light treatment can improve cognitive function by affecting the activity of neural circuits. ipRGC-SCN-CA1 and ipRGC-vLGN/IGL-Re-CA1 neural circuits were reported to involved in the cognition-improving effects of light treatment. Several neurotransmitters (acetylcholine, dopamine, norepinephrine, serotonin, gamma-aminobutyric acid), neurotrophic factors (brain-derived neurotrophic factor, nerve growth factor, and vascular endothelial growth factor) and hormones (corticotropin releasing hormone (CRH) and cortisol) also participated in the mechanisms of light treatment. Understanding these underlying mechanisms is crucial for comprehending the beneficial effects of light treatment on cognitive impairment. The article also discusses the limitations of light treatment in clinical applications, including standardizing light parameters and the impact of individual differences. The limitations of light treatment in clinical applications encompass standardized light parameters, individual differences, lack of long-term follow-up data, differences in research designs, and the absence of standardized treatment protocols. Overcoming these limitations requires further research and standardization efforts to ensure the reliability and effectiveness of light treatment in the management of cognitive impairment. This review aims to enhance our understanding of the advancements in light treatment for improving cognitive impairment and elucidate the underlying mechanisms involved. It also provides theoretical support for optimizing parameters and techniques in light treatment for cognitive impairment, thereby promoting its clinical application. Ultimately, this will contribute to further exploration of the potential of light treatment in the management of cognitive impairment associated with neurological and psychiatric disorders and advance related research endeavors.