The transcription factor C-Jun widely exists in vertebrates and invertebrates and plays an important role in various kinds of stimulus response. In this study, PmC-jun gene was first cloned from Penaeus monodon. The full-length cDNA of PmC-jun was 1857 bp in length and included an 879 bp open reading frame (ORF), which encoded 293 amino acids. qRT-PCR analysis results showed that PmC-jun mRNAs were ubiquitously expressed in all the examined tissues. The highest expression level was observed in gill, followed by hepatopancreas. The expression patterns of PmC-jun after Vibrio harveyi and Streptococcus agalactiae injections were studied by qRT-PCR experiment. PmC-jun increased obviously in the gill and hepatopancreas. The expression pattern of PmC-jun in the hepatopancreas was further studied using in situ hybridization (ISH) method. The mRNA expression level of PmC-jun significantly increased in the hepatopancreas after bacterial infection. The expression sites of PmC-jun were almost unchanged. PmC-jun played a regulatory role in pathogen invasion.