This review, within the One Health framework, compiles information on plant-derived bioactive compounds and emphasises their multifunctional role in improving environmental, animal, and human health. These compounds support sustainable health and ecological stability by influencing biological and environmental processes. Data from literature research are combined to explain the mechanisms and potential uses of different key bioactive compounds. Mechanistic insights focus on their capacity to regulate oxidative stress, inflammation, and microbial balance, linking these effects to therapeutic benefits in human health, enhanced animal productivity, and environmental sustainability. These compounds show antioxidant, anti-inflammatory, antimicrobial, and metabolic activities, helping prevent chronic diseases, strengthen immunity, and reduce reliance on antibiotics and pollution. Examples like quercetin, resveratrol, and curcumin demonstrate their roles in modulating inflammatory and metabolic pathways to foster sustainable health and ecological balance. Bioactive compounds are linked to the One Health strategy, providing benefits across biological systems. Nonetheless, challenges such as variability, bioavailability, and standardization remain. Future directions should aim to develop sustainable extraction and formulation methods, leverage omics technologies and artificial intelligence for discovery and characterization, and foster industry partnerships to validate these compounds and secure global regulatory approval.