LncRNA NEF has been proved to be a tumor suppressor in liver cancer. In the present study, we found that lncRNA NEF was downregulated and miRNA-155 was upregulated in plasma of triple-negative breast cancer (TNBC) patients compared with those in controls. These two factors were inversely correlated only in TNBC patients but not in controls. Altered expression of lncRNA NEF and miRNA-155 distinguished TNBC patients from healthy controls. Follow-up study showed that low level of lncRNA NEF and high level of miRNA-155 were correlated with poor survival. LncRNA NEF overexpression inhibited the migration and invasion of TNBC cells, while miRNA-155 overexpression promoted the migration and invasion of TNBC cells, but showed no significant effects on cancer cell proliferation. MiRNA-155 overexpression partially rescued the inhibited cell migration and invasion caused by lncRNA NEF overexpression. LncRNA NEF overexpression inhibited miRNA-155 expression, while miRNA-155 overexpression showed no significant effect on lncRNA NEF expression. Therefore, lncRNA NEF may participate in TNBC by negatively regulating miRNA-155.