This study was undertaken to isolate Actinomycetes from mangrove sediments of Tanzania and evaluate their potential for production of bioactive metabolites. Starch cacein agar medium was used to isolate the actinomycetes. Extraction of Actinomycetes using ethyl acetate (1:1), afforded dry extracts. The extracts were tested for antimicrobial activity and brine shrimp toxicity test. A total of three isolates (ACTN 1, ACTN 2 and ACTN 3) were obtained by using culture medium selective for Actinomycetes. Actinomycetes specific primers; S-C-Act-235-S-20 and S-C-Act-878-A-19 were used to identify two isolates as Streptomyces sp and one as actinomycetes sp. The strongest activity against bacterium (Bacillus subtillis) and fungus (Candida albicans) was exhibited by crude extracts of Streptomyces sp (ACTN 2 and ACTN 3). Crude extracts of all three isolates exhibited non- cytotoxic activity against brine shrimp larvae with LC50 values ranging from 250 - 446 μg/ml respectively. These results provide evidence that the mangrove sediments streptomycetes could be promising sources for antimicrobial bioactive agents.