Hemocytes of shrimp perform an essential role in defense against microbial pathogens, involving both cellular and humoral factors. The gene coding for ferritin in black tiger shrimp Penaeus monodon was cloned, sequenced and expressed using pQE-30-UA vector and SG13009 Escherichia coli host cells. The deduced amino acid sequence of P. monodon ferritin showed 32 to 95% similarity with ferritin proteins of other organisms. The recombinant protein was purified by nickel-nitrilotriacetic acid affinity chromatography. A single thick band of recombinant protein of approximately 21 kDa was observed in 15% sodium dodecyl sulfate polyacrylamide gel electrophoresis. Following mild acid treatment, 2 bands of ca. 14 and 7 kDa were produced; aspartine and proline acid cleavage sites were found at amino acid residues 123-124. The purified recombinant ferritin helped in reducing the mortality in shrimp infected with Vibrio harveyi . However, no direct antimicrobial activity against pathogenic V. harveyi was observed.