BACKGROUND: Deep vein thrombosis (DVT) is a vascular disease that has no effective treatment at present. Endothelial cells play a crucial role in the processes vasoconstriction, platelet activation, and blood coagulation and are an integral part of the vascular response to injury resulting in thrombus formation. OBJECTIVE: The aim of this study was to investigate the roles and mechanisms of long noncoding RNA LINC00659 (LINC00659) in endothelial cells. METHODS: The functions of LINC00659 and miR-525-5p on endothelial cells were explored by cell transfection assays, and the expression levels of LINC00659, miR-525-5p, and Bax in human umbilical vein endothelial cells (HUVECs) were assessed with reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR). Binding sites of LINC00659 and miR-525-5p were subsequently analyzed with bioinformatics software, and validated with dual-luciferase reporter gene assay. Effects of LINC00659 and miR-525-5p on proliferation and apoptosis of HUVECs were detected with MTT (3-(45)-dimethylthiahiazo (-z-y1)-35-di-phenytetrazoliumromide) assay and flow cytometry. RT-qPCR and western blot analysis were used to evaluate the mRNA and protein levels of apoptosis-related markers Bcl-2 and Bax in HUVECs. RESULTS: LINC00659 directly targeted and negatively regulated miR-525-5p, and Bax was a target of miR-525-5p. Upregulation of LINC00659 could inhibit proliferation and promote apoptosis of HUVECs, while the silencing of LINC00659 could increase the viability of HUVECs and inhibit apoptosis via upregulating miR-525-5p. Further mechanistic studies revealed miR-525-5p could negatively regulate Bax in HUVECs, and increased the viability of HUVECs and inhibited apoptosis by downregulating Bax expression. CONCLUSION: LINC00659 played an important role in DVT by regulating the apoptosis of vascular endothelial cells through regulating miR-525-5p/Bax axis.