Serum C-reactive protein (CRP) elevation predicts the development of heart failure in patients with hypertension. CRP activates macrophages and enhances oxidative stress. We hypothesize that CRP itself has a pathogenic role in the development of pressure overload-induced cardiac remodeling. Transgenic mice with human CRP overexpression (CRPtg) and nontransgenic littermates (CON) were subjected to transverse aortic constriction (TAC/CRPtg and TAC/CON) or sham operation (Sham/CRPtg and Sham/CON). One week after operation, in TAC/CRPtg, myocardial mRNA levels of interleukin (IL)-6, CD68, glutathione peroxidase-3 (GPx3), 47-kDa α-subunit of nicotinamide adenine dinucleotide phosphate oxidase (p47(phox)), and collagen-I, the number of infiltrating Mac-2-positive macrophages, nuclear localization of phosphorylated NF-κB/p65 (p-p65) in cardiomyocytes, nuclear NF-κB-DNA-binding activity, and reactive oxygen species (ROS) content were increased compared to those in TAC/CON. Cardiac fibrosis was more prominent in TAC/CRPtg compared to TAC/CON. Four weeks after operation, heart and lung weights, cardiomyocyte cross-sectional area, and the extent of cardiac fibrosis were greater in TAC/CON than in Sham/CON, and these differences were further augmented in TAC/CRPtg compared to TAC/CON. Left ventricular (LV) fractional shortening was less and LV end-diastolic pressure was higher in TAC/CRPtg than in TAC/CON. Myocardial mRNA levels of angiotensin type 1 receptor, atrial natriuretic factor, IL-6, GPx3, p47(phox), collagen-I, and transforming growth factor (TGF)-β1, the protein level of TGF-β1, and the numbers of Mac-2-positive macrophages and p-p65-positive cells were higher in TAC/CRPtg than in TAC/CON. In conclusion, CRP itself may have a pathogenic role in the development of pressure overload-induced cardiac remodeling, possibly through enhanced inflammation and oxidative stress.