Perfectionistic self-presentation is thought to confer risk for social anxiety. Although this relationship is thought to occur dynamically from moment-to-moment, no research has yet tested this relationship using experience sampling methods. The present study stringently tested whether perfectionistic self-presentation predicted social anxiety beyond several important covariates using a 21-day experience sampling design. A sample of 165 undergraduates (75.6% women) completed a series of questionnaires each day for 21 days using palm pilots. Generalizability theory and multilevel factor analyses suggested daily measures of perfectionistic self-presentation, social anxiety, perfectionism cognitions, and depressed mood evidence within-subjects and between-subjects variability, can be measured reliably, and represent distinct factors, allowing hypothesis testing. Multilevel regressions showed perfectionistic self-presentation predicted social anxiety at the between-subjects and within-subjects levels, even when controlling for socially prescribed perfectionism, perfectionism cognitions, and depressed mood. Overall, perfectionistic self-presentation emerged as a robust predictor of daily social anxiety, clearly extending prior cross-sectional research on this topic. By understanding how perfectionism operates from day-to-day, we can better understand the processes that give rise to social anxiety, and ultimately how to devise more effective ways to help people suffering from social anxiety.