Microglial dysfunction is a typical feature of Alzheimer's disease (AD); the key players include triggering receptor expressed on myeloid cells 2 (TREM2) and the transcription factor PU.1. However, the relationship between TREM2 and PU.1 remains obscure. In this study, we investigated the expression patterns of TREM2 and PU.1 in the 5×FAD mouse AD model. We found that the expression of TREM2 and PU.1 was significantly correlated with Aβ deposition in the brain in an incremental manner and that PU.1 promoted Aβ-induced TREM2 expression upregulation and potently impacted microglial phagocytosis. Notably, PU.1 interacted directly with the promoter region of TREM2 and increased its transcription, suggesting a direct regulatory mechanism. These findings provide new insights into the regulatory role of PU.1 in the transcription of TREM2 and emphasize the importance of TREM2 and PU.1 in microglial responses, highlighting their potential as therapeutic targets in AD treatment regimens.