Marine actinobacteria are the most economically and biotechnologically valuable prokaryotes receiving much attention for their capacities of antibiotics and enzyme inhibitors. A total of 142 endophytic actinomycetes was isolated from 44 samples of 5 different sponge species in Ha Tien Sea, Vietnam. Due to the antimicrobial activity, 21 isolates were selected for 16S rDNA sequencing. Of identified isolates 13 were characterized as Streptomyces spp. and the remainders belonged to other genera as Microbacterium, Rhodococcus and Gordonia. The antimicrobial activity and the amplifying genes coding for polyketide synthetase (PKS) and nonribosomal peptide synthetase (NRPS) showed that isolates purified from sponges in Ha Tien sea had broad-spectrum antimicrobial activity, mainly against gram-positive bacteria as Bacillus cereus and Staphylococcus aureus. Microbacterium tumbae was also found as a rare actinomycete displayed the antifungal activity. These new cultures can be employed as bioactive resources against pathogens, particularly in relation to food-borne diseases and human health.