Cinnamomum verum essential oil and its main component, cinnamaldehyde, were incorporated into nanoemulsions to improve their stability and activity. Oil-in-water (O/W) nanoemulsions were prepared using the high-energy ultra-sonication method. Cinnamon oil nanoemulsion exhibited a more vigorous DPPH radical scavenging activity (IC50 = 1.81 mg/L) than the standard Î±-tocopherol (IC50 = 9.16 mg/L). Cinnamaldehyde nanoemulsion exhibited the highest antibacterial action against Salmonella typhimurium and Staphylococcus aureus (MIC = 175 and 150 mg/L, respectively). It was also displayed the highest inhibition against Candida albicans (EC50 = 19.92 mg/L). Cinnamaldehyde nanoemulsion was the most active against mycelial growth of Aspergillus flavus and A. niger (EC50 = 38.20 and 134.80 mg/L, respectively). It also presented the highest activity against spore germination. This study describes antimicrobials and antioxidants based on nanoemulsions made from natural products that can be used to treat microbial infections.