Clostridium perfringens is a Gram positive anaerobic bacterium that causes a variety of diseases ranging from mild diarrhoea to clostridial myonecrosis. Previous studies comparing the transcriptomes of in vitro cultures of a human gas gangrene isolate to equivalent cells from myonecrotic muscle tissues revealed that several genes were up-regulated in infected muscle tissues. Among these genes, cppA and cppB were shown to be upregulated by log2 (fold-change) of 4.30 and 5.02, respectively, suggesting that they may play a role in disease pathogenesis. To investigate their role in virulence, independent ΔcppA, ΔcppB, and ΔcppAB mutants were constructed by allelic exchange and examined in the mouse myonecrosis model. Wild-type disease levels were observed in mice infected with the ΔcppB and ΔcppAB mutants. However, mice infected with the ΔcppA mutants were attenuated for virulence. These mice showed significantly improved survival compared to mice infected with the wild-type strain (log-rank Mantel-Cox test, p < 0.0001). Bioinformatic analyses suggested that these predicted CppA and CppB proteins may form fimbriae or may act independently as surface adhesins. Cell fractionation and Western blot analysis of a strain engineered to overexpress HA-tagged CppA showed that the CppA protein primarily localised to the membrane fraction. Stimulated emission depletion fluorescence microscopy on this strain showed that CppA is present on the surface of the bacterium. In conclusion, we have identified a novel surface protein, CppA, that appears to be required for virulence in C. perfringens-mediated clostridial myonecrosis.