Campylobacter jejuni is a leading cause of foodborne illnesses worldwide. Its porA gene encodes the major outer membrane protein (MOMP) that is abundantly expressed and has important physiological functions including a key role in systemic infection and abortion induction in pregnant animals. Despite the importance of porA in C. jejuni pathogenesis, mechanisms modulating its expression levels remain elusive. At the 3 prime end of the porA transcript, there is a Rho-independent transcription terminator (named TporA in this study). Whether TporA affects the expression and function of MOMP remains unknown and is investigated in this study. Green fluorescent protein (GFP) fusion constructs with the porA promoter at the 5 prime end and an intact TporA or no TporA at the 3′ end of the gfp coding sequence revealed that both transcript level of gfp and its fluorescence signals were more than 2-fold higher in the construct with TporA than the one without TporA. qRT-PCR analysis of the porA mRNA and immunoblotting detection of the MOMP protein in C. jejuni showed that disruption of TporA significantly reduced the porA transcript level and expression of the MOMP protein. mRNA decay assay demonstrated that disruption of TporA resulted in shortened transcript half-life of the upstream gfp or porA genes, indicating TporA enhances mRNA stability. In the guinea pig model, the C. jejuni construct with an interrupted TporA was significantly attenuated in abortion induction. Together these results indicate that TporA enhances the expression level of MOMP by stabilizing its mRNA and influences the virulence of C. jejuni.