The Impostor Phenomenon (IP) is often discussed as a problem in the field of computer science, but there has yet to be an empirical study to establish its prevalence among CS students. One survey by the Blind app found that a high number of software engineers at some of the largest technology companies self-reported feelings of Impostor Syndrome; however, self-reporting of Impostor Syndrome is not the standard diagnostic for identifying whether an individual exhibits feelings of the Impostor Phenomenon. In this work, the established Clance IP Scale is used to identify the prevalence of IP among graduate and undergraduate computer science students at a large research-intensive North American institution. Among this population of over 200 students, 57% were found to exhibit frequent feelings of the Impostor Phenomenon with a larger fraction of women (71%) experiencing frequent feelings of the Imposter Phenomenon than men (52%). Additionally, IP was found to have greater prevalence among computer science students than among students of other populations from comparable studies. Due to the negative impacts associated with feelings of the Impostor Phenomenon, computer science education should work to improve student awareness and help student cope with these feelings. CCS CONCEPTS • Social and professional topics → Computing Education.