Dickkopf-1 (DKK1) is a negative regulator of the Wnt/β-catenin signaling pathway, which is expressed in various human cancers. It was hypothesized that DKK1 was oncogenic and involved in invasive growth in non-small cell lung cancer (NSCLC) cells. The present study aimed to investigate whether DKK1 gene expression levels differ among various NSCLC cells. The DKK1 expression pattern was analyzed in various human NSCLC cell lines and tissues. The DKK1 protein and gene expression levels were quantified using immunoblotting, polymerase chain reaction analysis and immunohistochemistry. The majority of the lung cancer cell lines analyzed revealed increased expression levels of DKK1. Furthermore, DKK1 expression was highly transactivated in the majority of these cancer cell lines. Clinical samples were obtained from 98 NSCLC patients for immunohistochemical analysis. Of the 98 samples analyzed, 62 (63.3%) demonstrated positive staining for DKK1, whereas the remaining 36 (37%) exhibited negative staining. However, no immunohistopathological staining was detected in normal tissues. The relative effects of DKK1 were assessed in a high-expression cell line (LTEP-a-2) and a low-expression cell line (95D). The differential expression of genes involved in cell cycle, apoptosis, signaling pathway, invasion and metastasis were evaluated, relative to DKK1 levels. In conclusion, the results of the present study indicated that DKK1 functioned as a key regulator in the progression of NSCLC. The results confirmed the differential expression of DKK1 in NSCLC cells, which may present a potential therapeutic target for cancer prevention.