BACKGROUND: Lung cancer is the most common malignant tumor in China, lung adenocarcinoma (LUAD) is the main type of lung cancer, which is a serious threat to people's life and health. At present, there are fewer studies on the role of Dikkopf1 (DKK1) in lung adenocarcinoma. The aim of this study was to investigate the role and potential prognostic value of DKK1 in the development of lung adenocarcinoma by bioinformatics methods. METHODS: Several databases, such as genotype-tissue expression (GTEx), The Cancer Genome Atlas (TCGA) and tumor-immune system interactions database (TISIDB), were used to analyze the expression, clinicopathological features, immune cell infiltration, prognosis and methylation of DKK1 in lung adenocarcinoma. Then, linked immune cell infiltration Omics database was used to analyze the co-expressed genes of DKK1 and their functional enrichment. Finally, 59 pathological samples of paraffin-embedded lung adenocarcinoma patients who underwent surgery at the Affiliated Cancer Hospital of Xinjiang Medical University between 2016 and 2017 were collected for the validation of the prognostic value of expression by immunohistochemistry (IHC) test. RESULTS: The results of bioconfidence analysis showed that the expression level of DKK1 in lung adenocarcinoma tissues was higher than that in normal tissues, the expression in advanced cancers was higher than that in early stages, and the experimental validation revealed that among 59 cases of lung adenocarcinoma, there were 15 cases of negative expression (25.4%), 18 cases of weakly positive expression (30.5%), and 26 cases of strongly positive expression (44.1%). The different expression of DKK1 is related to methylation, prognosis and the activities of various immune cells. Functional enrichment shows that DKK1 may be involved in skin development and cell-substrate junction, and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis shows that DKK1 is related to ABC transporters. Bioinformatics analysis and clinical case specimens showed that high DKK1 expression was associated with poorer prognosis in patients with lung adenocarcinoma. CONCLUSIONS High expression of DKK1 in lung adenocarcinoma is associated with poor prognosis. DKK1 is closely associated with tumor immune cell infiltration and pathways. DKK1 can be considered as a potential prognostic marker and a novel target for immunotherapy of lung adenocarcinoma.