Diabetic retinopathy (DR) is a serious complication associated with diabetes, which may lead to diminished visual acuity or complete loss of sight. N6-methyladenosine (m6A) is recognized as the predominant modification present in eukaryotic mRNAs. However, the role of methyltransferase-like 3 (METTL3)-mediated m6A modification in DR still need further investigation. In our study, we constructed a DR cell model through the application of high glucose (HG) treatment on human retinal microvascular endothelial cells (hRMECs), and we found that METTL3 was downregulated for expression in the DR cell model. Mechanistically, we found that lncRNA MALAT1 was upregulated in hRMECs treated with HG due to the downregulation of METTL3 and subsequent reduction in m6A methylation. Functional experiments demonstrated that HG-induced upregulation of cell viability, endothelial-mesenchymal transition (EndMT), angiogenesis, and inflammatory factors were reversed by overexpressing METTL3, whereas these alleviating effects were neutralized by upregulation of MALAT1. Besides, inhibition of MALAT1 effectively attenuated retinal damage and inflammatory responses in streptozotocin (STZ)-induced DR mice. Furthermore, MALAT1 could act as a microRNA (miR)-23a-3p sponge to increase vascular endothelial growth factor A (VEGFA) expression. Reversal experiments indicated that knockdown of MALAT1 mediated DR alleviation effects were reversed by miR-23a-3p inhibitor or overexpression of VEGFA. In summary, our research findings indicated that silencing METTL3 reduced m6A modification of lncRNA MALAT1 and stabilized MALAT1 expression, thus promoted the growth, EndMT, angiogenesis, and inflammatory response of HG-induced hRMECs through the miR-23a-3p/VEGFA axis.