Among the sponge species collected in Southwestern Vietnam, Xestospongia testudinaria was relatively abundant but was less studied. Surveying the biological activities of sponges harvested at a depth of 10 m at Phu Quoc marine, Kien Giang province, gave lots of useful information. The extracts of this sponge species showed weak inhibition for bacterial and fungal strains (MIC > 512 µg/mL). The n-hexane extract exhibited two strains of Gram (-) bacteria including Staphylococcus aureus and Salmonella enterica with the values of IC₅₀ from 482.46±8.5 to 435.2±10.0 µg/mL. In addition, these sponge extracts showed moderate antioxidant activity with the values of EC₅₀ ˂ 300 µg/mL, in the ABTS assay.