Tumor necrosis factor-(TNF-)-α upregulates plasminogen activator inhibitor-(PAI-) 1 expression in pleural mesothelial cells (PMCs), contributing to fibrin deposition and pleural fibrosis. Histone deacetylases (HDACs) have been found implicated in fibrogenesis. However, the roles of TNF-α or HDAC in the regulation of PAI-1 expression have not been well investigated. We aimed to examine the effects and mechanisms of HDAC inhibition on TNF-α-induced PAI-1 expression in human PMCs. MeT-5A human PMCs were treated with TNF-α in the presence or absence of the m-carboxycinnamic acid bishydroxamide (CBHA), an HDAC class II inhibitor, and the HDAC activity, PAI-1 protein expression, mRNA, and activated signalings were analyzed. CBHA abrogated TNF-α-induced HDAC activity, PAI-1 protein and, mRNA expression in MeT-5A cells. Moreover, CBHA significantly enhanced mitogen-activated protein kinase phosphatase-(MKP-) 5/MKP-1 expression and inhibited p38/JNK activations, ATF2/c-Jun translocation, and PAI-1 promoter activity. Altogether, our data suggest that HDAC inhibition may abrogate TNF-α-activated MAPK/AP-1 signaling and PAI-1 expression in human PMCs. Given the antifibrotic effect through PAI-1 abrogation, CBHA may be utilized as a novel agent in the treatment of fibrotic diseases.