Plant secondary metabolites (SMs) are essential for plant defense and have diverse biological activities, making them valuable for medicine, food, and industry. Environmental factors such as light, temperature, soil water, fertility, and salinity significantly influence SM biosynthesis and accumulation. This review discusses how these factors affect SMs in plants, emphasizing their role in regulating plant metabolism and adaptation to environmental stresses. Light irradiation, temperature, soil water, fertility, and salinity all impact SM production, with variations in photoperiod, intensity, quality, and temperature affecting the levels of phenolics, flavonoids, terpenoids, and alkaloids. Soil water stress can increase SMs in some plants, while salinity can enhance phenolic compounds. Soil fertility influences SMs, with nutrient availability affecting flavonoids, alkaloids, and other compounds. The review highlights the importance of optimizing environmental conditions to enhance SM production for commercial and medicinal applications. Understanding these responses can help improve cultivation techniques and increase the yield and quality of bioactive compounds in plants.Plant secondary metabolites (SMs) are essential for plant defense and have diverse biological activities, making them valuable for medicine, food, and industry. Environmental factors such as light, temperature, soil water, fertility, and salinity significantly influence SM biosynthesis and accumulation. This review discusses how these factors affect SMs in plants, emphasizing their role in regulating plant metabolism and adaptation to environmental stresses. Light irradiation, temperature, soil water, fertility, and salinity all impact SM production, with variations in photoperiod, intensity, quality, and temperature affecting the levels of phenolics, flavonoids, terpenoids, and alkaloids. Soil water stress can increase SMs in some plants, while salinity can enhance phenolic compounds. Soil fertility influences SMs, with nutrient availability affecting flavonoids, alkaloids, and other compounds. The review highlights the importance of optimizing environmental conditions to enhance SM production for commercial and medicinal applications. Understanding these responses can help improve cultivation techniques and increase the yield and quality of bioactive compounds in plants.