The long non-coding RNA (lncRNA) NKILA (nuclear transcription factor NF-κB interacting lncRNA) functions as a suppressor in human breast cancer and tongue cancer. However, the clinical significance and biological roles of NKILA in esophageal squamous cell carcinoma (ESCC) remain unknown. In this study, we showed that NKILA was downregulated in ESCC tissues and cancer cells compared with their normal counterparts. Low NKILA expression correlated with large tumor size and advanced TNM stage, and predicted poor overall and disease-free survival of ESCC patients. Further loss- and gain-of-function assays indicated that NKILA inhibited proliferation and migration of ESCC cells in vitro, suppressed tumor growth and lung metastasis in vivo. Mechanistically, NKILA could inhibit phosphorylation of IκBα, suppress p65 nuclear translocation and downregulate the expression of NF-κB target genes in ESCC cells. These results suggest NKILA could suppress malignant development of ESCC via abrogation of the NF-κB signaling and may potentially serve as a prognostic marker for ESCC.