The harpacticoid copepod Tisbe biminiensis has been tested as live prey in marine crustacean and fish larviculture. The aim of the present study was to characterize the proteinases in the crude extract of T. biminiensis. Trypsin activity was assayed in the crude extract prepared by the homogenization of specimens reared under controlled laboratory conditions and fed on diatoms and commercial fish food. The physical-chemical and kinectics parameters were determined using BApNA as substrate. Optimal pH and temperature were 9.0 and 55°C, respectively. This enzyme was thermostable until 50°C. Using BApNA as substrate, the Km was 0.59 mM and the proteolytic activity was strongly inhibited by specific trypsin inhibitors. However, the presence of other proteases was observed using substrate-SDS-PAGE. Eight caseinolytic bands were observed in the zymogram, four of them were not inhibited by classical mammalian trypsin inhibitors. Trypsin from T. biminiensis showed similar properties to those described for species used in commercial aquaculture. These results demonstrate that T. biminiensis may be a source of proteases, including trypsin-like enzymes.