An L-amino acid oxidase (LAAO) from Crotalus durissus cumanensis venom (CdcLAAO) was purified to homogeneity using a combination of size-exclusion and ion exchange chromatographies. CdcLAAO is a monomeric protein exhibiting an apparent molecular mass of 55 kDa and a calculated pI of 8. Its complete 498-amino-acid sequence was deduced through cDNA and protein sequencing. The enzyme oxidized L-Leu with Km and a VMax of 9.23 μM and 0.46 μM/min respectively, and exhibited Kcat and a Kcat/Km of 1.8 s−1 and 195 mM−1s−1. CdcLAAO inhibited in a dose-dependent manner the growth of Staphylococcus aureus and Acinetobacter baumannii. The inhibitory effect was more significant on S. aureus, with a Minimal Inhibitory Concentration (MIC) of 8 μg/mL and Minimal Bactericidal Concentration (MBC) of 16 μg/mL, than against A. baumannii, with a MIC of 16 μg/mL and MBC of 32 μg/mL. However, against Escherichia coli CdcLAAO did not show inhibitory capacity at the concentrations tested (2–128 μg/mL). CdcLAAO did not exhibit cytotoxic activity on the mouse myoblast cell line C2C12 and on peripheral blood mononuclear cell (PBMC).