Recent studies implied a significant role of hypoxia-inducible factor-1α (HIF1α) in cell transformation. This study aimed to assess the effects of HIF1α on the epithelial–to–mesenchymal transition (EMT) and tumorigenesis of lung adenocarcinoma cells. Invasion, migration and colony formation assays were used to evaluate cell transformation. Expression of EMT-related markers were analyzed by western blot, reverse-transcription polymerase chain reaction or zymography. A luciferase assay was carried out to access the transcriptional activity of β-catenin. Hypoxia enhanced migration, invasion and transformation of A549 lung adenocarcinoma cells. Hypoxic stimulation promoted the expression of EMT-related markers in lung cancer cells. The expression of HIF1α was found to be involved in hypoxia-mediated modulation of expression of snail family transcriptional repressors 1 (SNAI1) and 2 (SLUG). Hypoxia enhanced nuclear accumulation and transcriptional activity of β-catenin. β-Catenin promotes expression of EMT-related genes and eventually contributes to the metastatic process.