Koelreuteria plants have been used as a Chinese and Taiwanese folk medicine for the treatment of hepatitis, enteritis, cough, pharyngitis, allergy, hypertension, hyperlipidemia, diarrhea, malaria, urethritis and eye related diseases. The plants are distributed in Taiwan, Fiji, Northern China, Korea and Japan. The present study focused on the phytochemistry and pharmacological activities of the genus Koelreuteria to explore active constituents, therapeutic activities, and outlook for research. Extracts and essential oils of the genus Koelreuteria showed variety of bioactive metabolites including phenolic acids, flavonoids, lignans, steroids, terpenoids, etc. Scientific studies on extracts and essential oils demonstrated a range of pharmacological actions, as anticancer, antioxidant, antibacterial, antifungal, anti-hyperlipidemia, hepatoprotective and anti-Alzheimer's disease. Some indications have been verified through pharmacological activities, such as protein tyrosine kinase (PTK), topoisomerase 1, dihydrodiol dehydrogenase (DDH) protein expression, xanthine oxidase (XOD), tyrosinase, lipoxygenase and human low-density lipoprotein (LDL) inhibitory activities and induction of heme oxygenase-1 (HO-1) by this genus. The accessible literature revealed that, most of the genus activities could be attributed to the active flavonoids, lignans, terpenoids and essential oil. However, to confirm their pharmacological activities against human cancer cell lines and microbial diseases, more investigations are necessary to evaluate the molecular mechanisms of the identified active compounds. More evaluations and clinical trials should be carried out that might be incorporated into medicinal practices.