Numerous stressors, such as test anxiety, imposter phenomenon, and perfectionism. The association between the imposter phenomenon and perfectionism is well-studied, but test anxiety as a mediator of this association is not examined. The present study aimed to explore the mediating role of test anxiety on the imposter phenomenon and perfectionism among Pakistani high-achieving students. Additionally, we investigated gender and grade differences for junior and senior high school students. In the present cross-sectional survey study, participants (n = 250) aged 15-18 years responded to the Clance Imposter Phenomenon Scale, Frost Multidimensional Perfectionism Scale, and Westside Test Anxiety Scale. Findings showed that perfectionism increased by 39% with a one-unit increase in the imposter phenomenon. Test anxiety was a significant positive mediator of the association between imposter phenomenon and perfectionism. T-test showed girls had higher scores on the imposter phenomenon and test anxiety than boys. One-way ANOVA revealed significant educational grade differences with small effect sizes, and junior high school students scored higher than senior high school students on study variables. About 44% and 48% of 250 participants reported having moderate and frequent imposter symptoms, respectively. Almost 36.5% of high-achievers had low test anxiety, and 50% of high-achievers had normal test anxiety. The study presents a discussion of the merits and demerits.