Water in hydrothermal condition has been used for extraction of nutraceutical compounds from Chlorella vulgaris. Hydrothermal extraction was carried out in a semi-batch and a batch extractor at various temperatures (120-200C), pressures (2-10MPa), and extraction times (30-300min) to extract antioxidant and antibacterial compounds. The effect of extraction condition on the yield of extract was investigated. The antioxidant and antibacterial activity of extracts obtained by hydrothermal extraction were examined. The increasing extraction temperature resulted in higher antioxidant activity, but lower antimicrobial activity. As comparison with hot water extraction, the antioxidant activity of extract obtained by hydrothermal extraction was higher than that obtained by hot water extraction, but the antibacterial activity of the extract obtained by hydrothermal extraction was lower.