Anxiety is highly prevalent among adults. Evidence suggests that perceived stress controllability and emotional growth mindsets are associated with decreased anxiety. However, whether these positive factors synergistically contribute to reducing the impact of stress on anxiety remains unclear, especially within everyday stress contexts. Multilevel models were used to investigate how perceived stress controllability and emotional growth mindsets interacted to mitigate the adverse impact of daily stress on anxiety, differentiating within- and between-person effects. Overall, 198 participants completed ecological momentary assessments of perceived stress intensity and controllability, emotional growth mindsets, and anxiety four times daily over 10-12 consecutive days. The within-person analyses showed that high emotional growth mindsets buffer the link between perceived stress intensity and anxiety. More importantly, the between-person and cross-level results suggested that the synergistic effect of emotional growth mindsets and perceived stress controllability maximally buffered the correlation between perceived stress intensity and anxiety. Additionally, these results highlighted that the positive association between perceived stress intensity and anxiety was most pronounced among participants with low emotional growth mindsets and perceived stress controllability. These findings further support a synergistic intervention approach that emphasizes anxiety alleviation through enhanced perceived stress controllability and the development of emotional growth mindsets.