Background Lung cancer is one of the tumors with high morbidity and mortality among males and females worldwide. Proline-, glutamic acid-, and leucine-rich protein 1(PELP1) is an estrogen receptor coactivator and functions as a scaffolding protein. Its oncogenic signaling was involved in the progression of several cancers. However, there is little known about the role of PELP1 in the lung cancer. The aim of this study is to explore the role of PELP1 in non-small cell lung cancer. Methods The expression of PELP1 in microarrays of lung cancer tissue and correlation with clinicopathological parameters were performed. RNA interference technology was used to downregulate PELP1 expression in A549 lung cancer cells and the tumor cell’s ability of proliferation, migration, invasion was detected by Cell Count Kit-8 and trans-well essay. In addition, whole genome exon was analyzed by poly-A RNA-sequencing. Results Results showed that PELP1 is overexpressed in the lung cancer specimens and its expression correlate with histological type, smoking status, and EGFR status but no significant prognostic value. Knockdown of PELP1 inhibited cell proliferation, migration, invasion of lung cancer cells. Furthermore, silencing PELP1 in lung tumor cells promotes the sensitivity of tumor cells to the tyrosine kinase inhibitor Gefitinib. RNA-sequencing and Western-blotting found that 140 genes were up-regulated and 143 genes were down-regulated in PELP1 silenced lung adenocarcinoma cells, which mainly affected the mitogen-activated protein kinase (MAPK) signal pathway, EGFR tyrosine kinase inhibitor resistance, PPAR signaling pathway, Cytosolic DNA-sensing pathway, cytokine-cytokine receptor interaction, drug metabolism, cAMP signaling pathway, RIG-1-like receptor signaling pathway. Conclusions PELP1 plays a key role in non-small cell lung cancer proliferation, progression, and drug resistance. These results suggest that PELP1 could be a potential target for therapeutic intervention for lung cancer.