The biological activities of Laurencia obtusa and Laurencia obtusa var. pyramidata from Cesme coasts (Turkey) were screened by using in vitro methods. The essential oils of L. obtusa and L. obtusa var. pyramidata were obtained by steam distillation and their chemical compositions were analyzed by GC/MS. The antimicrobial activities against bacteria (two specific pathogenic strains (methicillin-oxacillin resistant Staphylococcus aureus ATCC 43300, hemorrhagic Escherichia coli (O157: H7) RSSK 232)) and one yeast strain (Candida albicans ATCC 10239) were determined by using the disc-diffusion technique. The antimicrobial potential of the L. obtusa essential oil was found considerably strong. It showed inhibitory effect on two bacteria and one yeast strain. The hexane and chloroform extracts of L. obtusa and the methanol and chloroform extracts of L. obtusa var. pyramidata were generally found as moderate antioxidants in comparison with butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and alpha-tocopherol (Vitamin E). The chloroform extracts of both the red algae have high phenolic content compared to the other extracts and essential oils.