We conducted an event-related potential (ERP) study using a 256-channel dense sensor array electroencephalography (EEG) system to examine how, and if the P200 neurophysiological signal is sexually dimorphic. We had two groups of participants: females (n= 15, mean age = 40.6 years old) and males (n = 15, mean age = 39.0 years old). ERPs from all participants were recorded while the participants performed an oddball task. Results showed that males on average had a significantly larger P200 peak amplitude and a significantly shorter P200 latency period. These results indicate that the P200 ERP is affected by sex. Therefore, suggesting that sex differences exist on an electrophysiological level, which may aid in better understanding of sex-biased biological influences, behaviors, neuropsychiatric disorders, and general brain function.