Plant galls, induced by a variety of organisms such as insects, mites, and fungi, are crucial in plant ecology, evolution, and human culture. These galls are rich in secondary metabolites (SMs), which include phenolic compounds, terpenes, and other bioactive molecules. Phenolic compounds, particularly tannins, and flavonoids, are commonly found in galls and have been associated with defensive functions against herbivores and pathogens. Recent studies highlight their antioxidant functions, helping the plant cope with oxidative stress during gall formation. The distribution and concentration of these compounds can vary depending on factors such as the physiological status of the host plant, gall developmental stages, and the specific galling organism involved. Volatile compounds, including terpenoids, are also present in galls, influecing plant-insect interactions. Galling organisms can modify the profile and concentration of volatiles in their host plants, influencing the attraction of female insects and the selection of oviposition sites. Their impact on volatile emissions varies; some studies note decreases while others report increases. Besides ecological roles, humans use plant galls medicinally due to their polyphenol-rich content, valued for antioxidant, anti-inflammatory, and anticancer properties. Edible galls, like those from certain fungi, are consumed in various cultures. Additionally, plant galls have been explored for their allelopathic potential, affecting the growth and development of neighboring plants. Understanding the chemical composition of galls and their impact on host plant properties provides valuable insights into plant defense mechanisms, ecological dynamics, and potential applications in human cultures.