<p>Post-event processing (PEP) is a key maintaining factor in social anxiety disorder (SAD). Cognitive models of SAD propose that socially anxious individuals engage in more maladaptive cognitive processing following social events, with these thoughts becoming increasingly negative and distorted over time. Although numerous studies have reported a positive association between PEP and SAD, research that examines PEP across an extended time period using a performance task remains limited. The present study aims to investigate changes in PEP over time among individuals with high and low levels of social anxiety, and to examine the mediating role of objective performance in the relationship between fear of positive evaluation (FPE) and PEP. Participants (<i>N</i> = 170) completed the Liebowitz Social Anxiety Scale (LSAS), the Brief Fear of Negative Evaluation Scale (BFNE), and the Fear of Positive Evaluation Scale (FPES), followed by an impromptu speech task delivered in front of a camera. PEP measures were collected weekly over a one-month period following the speech. In addition, independent observers rated participants’ speech performances based on video recordings. ANOVA results indicated that PEP scores decreased over time in both high and low social anxiety groups; however, individuals with high social anxiety consistently reported significantly higher levels of PEP throughout the study period. Bootstrap analysis further revealed that objective performance mediated the relationship between FPE and PEP, controlling for fear of negative evaluation (FNE). These findings enhance our understanding of the temporal dynamics of PEP in individuals with varying levels of social anxiety and highlight the roles of FPE and objective performance on post-event cognitive processes. Implications of these results are discussed in the context of existing literature on social anxiety.</p>