There are limited data available in the literature about the frequency and distribution of endocarditis in suckling and weaned piglets. The goal of this study was to investigate the frequency and distribution of lesions from cases of spontaneous valvular endocarditis in young piglets and to determine the bacterial agents involved in those lesions. Valvular endocarditis lesions in suckling piglets were detected in 21/454 cases (4.62%) and in 20/306 cases (6.53%) in weaned piglets. Streptococci were the dominant bacterial species isolated in 68% of the cases; S. suis was identified in 48.7% of the cases, S. pyogenes in 7.3% and S. spp., which could not be further identified, were cultured in 12.1% of the cases. E. rhusiopathiae was identified as the causal agent of endocarditis in four cases in the weaned piglets. In three cases, A. suis and S. aureus were isolated, and, in two cases, A. pleuropneumoniae was identified. Y. enterocolitica was isolated form one case of valvular endocarditis in a weaned pig. The finding of valvular endocarditis caused by Y. enterocolitica is an uncommon finding in pigs, and to the authors’ knowledge, there are no other reports of this agent being the cause of endocarditis in pigs. The involvement of Y. enterocolitica in endocarditis might have been assisted by the predisposing role of immunosuppressive viruses, such as porcine reproductive and respiratory syndrome.