Despite effective antiretroviral therapy (ART), people with HIV (PWH) experience persistent inflammation and metabolic dysfunction, increasing their risk for non-AIDS comorbidities. Accordingly, we evaluated the effects of long-term/low-dose Δ9-tetrahydrocannabinol (THC) supplementation in simian immunodeficiency virus (SIV)-infected, ART-treated rhesus macaques (RMs). THC significantly increased plasma/jejunum serotonin and indole-3-propionate, enhancing gut-brain communication through up-regulation of serotonin receptors (HTR4/HTR7) and aryl hydrocarbon receptor (Ahr) signaling via a cannabinoid receptor (CBR)-2-mediated mechanism. Furthermore, THC enriched cholesterol-metabolizing Oscillibacter and reduced plasma cholesterol and toxic secondary bile acids (SBAs), thus improving cholesterol and SBA homeostasis. Furthermore, THC increased β-hydroxybutyrate (BHB) levels via a CBR1-mediated mechanism, suggesting enhanced hepatic fatty acid oxidation for metabolic and cardiovascular health. THC restored ART/SIV-induced elevation of pro-inflammatory and cardiotoxic long-chain acylcholines to preinfection levels. THC-treated RMs maintained viral suppression despite reduced plasma ART levels, suggesting diminished ART-related toxicity. Our findings demonstrate phytocannabinoids to be a safe adjunct therapy alongside ART to mitigate chronic inflammation and metabolic dysfunction in PWH.