The aim of this study was to investigate the overall effects of phototherapy on biopterin (BH4), neopterin (BH2), tryptophan (Trp), and behavioral neuroinflammatory reaction in patients with post-stroke depression. There involved a total of 100 hospitalized patients with post-stroke depression at our hospital from February 2021 to December 2022. The participants enrolled were randomly assigned to either the control group or the experimental group. The control group received routine treatment, including medication and psychological support, while the experimental group received 30 min of phototherapy daily for 8 weeks. All participantsvoluntarily participated in the study and provided informed consent. Baseline characteristics of the patients were statistically analyzed. The severity of depressive symptoms was evaluated using the hamilton depression scale (HAMD) and the beck depression inventory (BDI). Levels of amino acid neurotransmitters, including gamma-aminobutyric acid (GABA), aspartic acid (Asp), and glutamic acid (Glu), were measured using radioimmunoassay. Plasma levels of neuroinflammatory factors, such as TNF-α, IL-6, and IL-1β were, determined using ELISA. Plasma levels of BH4, BH2, and Trp were detected by HPLC. Levels of SOD, GPx, CAT, and MDA in plasma were measured using corresponding kits and colorimetry. Quality of life was assessed using the SF-36 scale. There were no differences in baseline characteristic between the two groups (P > 0.05). The HAMD and BDI scores in the experimental group were lower than those in the control group (P < 0.05), indicating phototherapy could reduce the severity of post-stroke depression. The levels of GABA, Glu, and Asp in both groups significantly increased after treatment compared to their respective levels before treatment (P < 0.01).The levels of GABA in the experimental group were higher than those in the control group (P < 0.01),while the levels of Glu, and Asp were lower than those in the control group (P < 0.01). The plasma levels of TNF-α, IL-6, and IL-1β in the experimental group were evidently lower than those in the control group (P < 0.05). Moreover, the levels of BH4 and Trp in experimental group were significantly higher than those in the control group (P < 0.05), while the levelsof BH2 in the experimental group were significantly lower than the control group (P < 0.05). Additionally, the levels of SOD, GPx, and CAT in the experimental group were evidently higher than those in the control group (P < 0.05), whereas the levels of MDA in the experimental group were significantly lower than control group (P < 0.05). The experimental group showed higher scores in physical function, mental health, social function, and overall health compared to the control group (P < 0.05). Phototherapy exerted a profound impact on the metabolism of BH4, BH2, and Trp, as well as on behavioral neuroinflammatory reactions and the quality of life in patients suffering from post-stroke depression. Through its ability to optimize the secretion and synthesis of neurotransmitters, phototherapy effectively regulated neuroinflammatory reactions, improved biochemical parameters, enhancedantioxidant capacity, and alleviated depressive symptoms. As a result, phototherapy was considered a valuable adjuvant therapeutic approach for patients with post-stroke depression.