Background Alzheimer's disease (AD) is a progressive neurodegenerative disease in the elderly. MicroRNA (miRNA) miR-212-3p (miR-212) has been reported to dysregulated in many neurodegenerative diseases including AD. However, the mechanism and function of miR-212 in AD has not been reported. Methods The levels of miR-212 and PDCD4 in AD patients and A beta(25-35)-treated SH-SY5Y and IMR-32 cells were measured by qRT-PCR and/or Western blot. The putative target of miR-212 was predicted by DIANA tools online database and the interaction between miR-212 and PDCD4 was validated by dual luciferase reporter assay and RNA pull-down assay. The cell proliferation, cell apoptosis and the protein levels of Bcl-2, Bax, Cleaved caspase 3, p-PI3K, PI3K, p-ATK and ATK were measured by MTT assay, flow cytometry and Western blot. Results The level of miR-212 was apparently down-regulated, and the level of PDCD4 was significantly up-regulated in plasma from AD patients and A beta(25-35)-treated SH-SY5Y and IMR-32 cells. Following a dual luciferase reporter assay verified the direct interaction between miR-212 and PDCD4. The RNA pull-down assay further validated this interaction. The functional experiment indicated that PDCD4 mitigated the promotion effects on cell viability, the apoptosis-inhibited protein Bcl-2, the ratio of p-PI3K/PI3K, p-ATK/ATK and the suppressive effects on cell apoptosis and the corresponding protein levels of Bax, Cleaved caspase 3 caused by miR-212 mimics. Conclusion All the data in this study revealed that miR-212 modulated PDCD4 to regulate cell proliferation, apoptosis through PI3K/AKT signaling pathway in A beta(25-35)-treated SH-SY5Y and IMR-32 cells, and this new regulatory network may provide a novel mechanism of AD.