Relaxin (RLX), reported to play an important role in cardiovascular remodeling, is linked to activation of matrix metalloproteinases (MMPs). Interruption of the cardiac Wnt/β-catenin signaling system is reported to have antihypertrophic effects. Thus, the objectives of this study were to determine the effects of RLX on the myocardial Wnt/β-catenin signaling system and MMP expression in the postnatal day 2 (PND 2) porcine heart. Results showed that myocardial Wnt7a and Wnt4 gene expression at PND 2 decreased following treatment with RLX in vivo from birth, while there was no effect on Wnt5a expression. Immunoreactive myocardial β-catenin protein was reduced in RLX-treated animals. Zymographic analysis of medium from RLX-treated heart explants showed an increase in pro-MMP-2 but not pro-MMP-9 activity. Western blot analysis indicated that RLX increased myocardial MMP-2 protein compared to controls. Data suggest that the RLX-induced decline in Wnt/β-catenin expression at PND 2, together with increased MMP-2 activity, may be important for neonatal porcine cardiac remodeling.