Chitin, a homopolymer of N-acetyl-D-glucosamine (GlcNAc) residues linked by beta 1-4 bonds, is the most abundant renewable natural resource after cellulose. It is widely distributed in nature as the integuments of crustaceans and insects and as a component of fungi and algae. This study investigated the effects of a bifunctional chitinase/lysozyme-producing strain, Pseudomonas aeruginosa K-187, on degradation of shrimp shells and the survival conditions of bacterial strains in mangrove river sediment of Tamsui River. The structures of the whole bacterial community of the samples were measured by using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique. Results show that three bacterial strains (Acrobacter sp., Shewanella sp., and Marinobacterium sp.) which originated from the mangrove river sediment were found predominant in the 6 days-incubation sample of P. aeruginosa K-187 amended mangrove river sediment. Meanwhile, biomass, reducing sugar, and total sugar were found highest in the 6 weeks-incubation sample of shrimp shell powder and P. aeruginosa K-187-amended mangrove river sediment. According to the results, we assumed that the amendment of P. aeruginosa K-187 can enhance the biodegradation of shrimp shells in the seawater containing mangrove river sediment. We hope that these findings may provide some useful information for the reclamation of chitin-containing wastes in our environment.