The nipah worm (Namalycastis rhodochorde) is one of the polychaeta species lived in the Nypha fruticans mangrove mud of  West Kalimantan that has  potentialy to be cultivated. Feed aspect is an important part of cultivation, through improving the quality of feed by giving probiotics that are able to produce secondary and primary metabolites derived from the microflora of nipah worms. These metabolites are expected to increase their immunity and biomass. The purpose of this study was to determine the composition and characteristics of actinomycetes derived from mangrove substrate, gastrointestinal and feces of nipah worm. Isolation of actinomycetes was carried out by pour plate method on Starch Casein and Glycerol Asparagine Agar. Characterization process was carried out by growing isolates on ISP2, ISP3, ISP4 and ISP5 agar with the addition of starch, cellulose, and milk casein based on Bergey’s Determinative Bacteriology protocol for actinomycetes. The results showed that the highest actinomycetes density was found in mangrove mud (3.3 × 10⁴ CFU/10 g). Twelve actinomycetes had been characterized. Seven isolates from mangrove substrate, four isolates from feces and one isolate from the gastrointestinal tracts. All isolates were closely related to Streptomyces genera.