Lung adenocarcinoma is the leading cause of cancer-related death worldwide. The aim of the present study was to investigate the potential function of endoplasmic reticulum protein 29 (ERp29) in lung adenocarcinoma. We examined the expression of ERp29 in 75 patients with lung adenocarcinoma by immunohistochemical analysis, as well as its association with clinicopathological features. We further tested the effects of inhibiting ERp29 on cell proliferation, migration ability, and chemosensitivity to gemcitabine in human lung adenocarcinoma cell lines. ERp29 was significantly overexpressed in lung adenocarcinoma when compared with matched nontumor tissues. However, we did not observe significant associations of ERp29 with any of the clinicopathologic characteristics, including sex, age, differentiation, tumor, node, and metastasis stage, T stage, and lymph node metastasis. Downregulation of ERp29 by small interfering RNA did not affect cell growth, but impaired cell migration of lung adenocarcinoma cells. Inhibition of ERp29 significantly enhanced the chemosensitivity of lung adenocarcinoma cells to gemcitabine. These results support a probable treatment combination of gemcitabine and inhibition of ERp29 overexpression for lung adenocarcinoma to promote the clinical curative effects.