The recent appearance of growing number of bacteria resistant to con ventional antibiotics has stimulated the search for novel antimicrobial compounds from variety sources including marine sources. Four genera of marine invertebrates were collected from Tabuk region, Kingdom of Saudi Arabia. Bioactive metabolites were extra cted using methanol and tested for its activity against sets of Gram +ve bacteria, Gram - ve bacteria, yeast and fungi using the agar disk diffusion method. The results showed different patterns of antibacterial activity. About 75% of the marine invertebrate extracts presented significant activity against yeast. No activity shown with fungi. These findings suggest that the marine invertebrates are a potential source of novel antimicrobial compounds. These results in relation with antibacterial and antiyeast a ctivities in vitro open the way for complementary investigation in order to purify and identify active molecules.