Background/Objectives: Imposter Phenomenon (IP) describes internal doubt and fear of being exposed as fraud despite achievements. Coined by Clance and Imes, it is linked to societal pressures and attributing success to luck rather than ability. The main aim of this study was to investigate the prevalence and factors associated with IP among Alfaisal University medical students. Methods: A cross-sectional study was conducted using a self-reported questionnaire to assess IP and perfectionism in 295 medical students (74.9% female). Descriptive statistics and regression analyses were used to analyze the data. Results: Nearly half (49.2%) of the participants reported frequent imposter characteristics, with a substantial portion (27.1%) experiencing intense characteristics. Females were more likely to experience IP compared to males. Neither GPA nor year of study were significant predictors of IP. However, perfectionism scores showed a strong positive association with IP. Conclusions: This study identified a high prevalence of IP among Alfaisal medical students. While gender differences were observed, academic performance and year of study were not significant predictors. Perfectionism emerged as an associated factor of IP. These findings suggest that interventions targeting perfectionism and promoting self-compassion may benefit medical students experiencing IP. Further research is needed to explore the underlying causes of IP and its impact on student well-being.