Socotra Island (Yemen) is one of the best environments where many medicinal plants grow. Dracaena cinnabari (DC) grows there & widely used in folk medicine. This work aimed to analyze the plant chemically & to study the biological effects of some of its purified compounds & aqueous extract (AE) on rat isolated smooth muscles (ISM), perfused heart (PH), blood pressure (BP) and diuresis. Chemical analysis of the resin of DC resulted in the isolation of 5 flavonoids: 4,4’-dihydroxy-2’-methoxychalcone, 4,4’-dihydroxy-2-methoxydihydrochalcone, 7-hydroxy-3-(3-hydroxy-4-methoxybenzyl) chroman, 7-hydroxy-3-(4-hydroxybenzyl) chroman, and 2’,4,4’-trihydroxychalcone. The last compound was isolated for the 1st time from DC. The 1st two compounds had a concentration dependent (CD) effect on rat ISM. Also, it had a CD stimulatory effect on the contractility & an inhibitory effect on heart rate of isolated PH. In addition, it reduced the arterial BP & caused an increase in the rate of urine excretion. The AE of DC caused similar results. Finally, the effects of AE of DC & some of its purified compounds on rat ISM, PH, BP & diuresis are well consistent with the use of this plant in folk medicine.