Microalgae are very important organisms because of their biochemical contents. They can be used many areas such as industrial applications, agriculture, human and animal nurtrition etc. When the increasing population is considered, the humanity will need more nutrient. At this point; microalgae help us because they have essential amino acids, fatty acids and the other biochemical molecules that obligatory for human and animal nutrition. In this study; biochemical properties such as total protein amount, total oil amount, types and amounts of fatty acids, vitamin A, E and beta-Carotene amount of Tetracystis isobilateralis R. M. Brown & H. C. Bold were examined by using gas chromatography. Analysis has shown that total protein amount was 38.73%; total oil amount was 16.37%; vitamin E amount was 301.8 mg/kg, vitamin A amount was 28.40 mg/kg and beta-carotene amount was 815.4 mg/kg. Amounts of palmitic, linoleic, oleic, stearic fatty acid types were found to be 40.99%, 6.34%, 35.89% and 16.64% respectively.