Epithelial to mesenchymal transition (EMT) is a complex and dynamic molecular event in lung cancer metastasis that has not yet been thoroughly investigated. EMT transcriptional factors, such as Snail, play a central role in regulation of the EMT process. In this study, we sought to identify an association between p300 and Snail in lung cancer, as well as the engagement of p300 in Snail acetylation. We transfected p300 small interfering RNA into lung cancer cells to detect Snail and E-cadherin expression levels by real time-PCR. Immunoprecipitation assay was conducted to determine Snail acetylation in vivo. Bacteria-expressed Snail was purified to analyze Snail acetylation in vitro. We further mutated lysine 187 for identifying acetylated residue in Snail. Snail transcription in lung cancer cells was repressed by p300 knockdown. E-cadherin expression was increased by transfection of p300 small interfering RNA in a dose-dependent manner. Immunoprecipitation and Western blot assay with anti-acetylated lysine antibody were used to confirm that Snail was acetylated by p300. A sequence coding snail gene was cloned into glutathione S-transferase-tagged vector and the fusion protein was purified using glutathione. We observed Snail acetylation in vitro by incubation of recombinant Snail and p300 histone acetyltransferase domain with acetyl coenzyme A. The reduced Snail acetylation level was related to lysine mutation at position 187 of Snail. There was a correlation between Snail and p300 expressions in lung cancer. Moreover, p300 acetylates Snail both in vivo and in vitro, and K187 may be involved in this modification. © 2017 The Authors. Thoracic Cancer published by China Lung Oncology Group and John Wiley & Sons Australia, Ltd.