Content of essential oils in flower and leaf of Citrus microcarpa was 1.1 and 0.8% (v/w), respectively. The flower oil was dominated by monoterpene hydrocarbons in which limonene (74.5%) was determined as a major component. The dominant constituents found in the calamondin leaf oil were sesquiterpene (82.0%) with elemol (37.5%) as a major component. The obtained thermal data showed that thermal stability of flower and leaf oils was up to 80 and 110 °C, respectively. A study of TG isothermal volatilization at 42.5 °C showed the mass loss of the essential oils as a function of exposition time. Antioxidant assays using both DPPH and ABTS radical scavenging methods exhibited antioxidant activity of flower and leaf essential oils was higher than that of vitamin C. The leaf essential oil exhibited inhibitory effects against six microbial strains while the flower oil inhibited only one fungus strain, A. niger.