Recently, novel non-pharmacological interventions, such as photobiomodulation (PBM) therapy, have shown promise for the treatment of Alzheimer’s disease (AD). This article outlines the translation from the preclinical to clinical stages of an innovative brain–gut PBM therapy in a mouse model of AD, a pilot clinical trial involving mild-to-moderate AD patients, and a continuing pivotal clinical trial with a similar patient population. In a mouse model of AD (A\beta{}_{25-35}), daily application of brain–gut PBM therapy to both the head and the abdomen produced a neuroprotective effect against the neurotoxic effects of an A\beta{}_{25-35} peptide injection by normalizing all the modified behavioral and biochemical parameters. The pilot clinical trial to evaluate brain–gut PBM therapy demonstrated the tolerability and feasibility of the novel PBM-based treatment for mild-to-moderate AD patients. Compared to the sham patients, the PBM-treated patients had lower Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS-Cog) comprehension sub-scores, higher forward verbal spans, and lower Trail Making Test (TMT) Part B (TMT-B) execution times, which suggest an improvement in cognitive functions. This pilot study provided important information for the design of a novel pivotal clinical trial, currently in progress, to assess the efficacy of brain–gut PBM therapy in a larger sample of AD patients. This pivotal clinical trial could demonstrate that brain–gut PBM therapy is a safe, well-tolerated, and efficient disease-modifying treatment for mild-to-moderate AD patients and that it has medical and economic benefits.