Resistin is considered to be a risk factor for several types of cancer, but its functions are controversial and not well studied in lung cancer. The present study is aimed to investigate the expression of resistin in lung adenocarcinoma tissues, in order to evaluate its association with the clinicopathological characteristics of cancer patients and to investigate the effects of resistin in lung adenocarcinoma cells. A total of 70 pairs of lung adenocarcinoma tissues and normal tissues were collected and immunohistochemistry was performed to examine resistin expression. Resistin overexpressed cells were established by plasmid transfection in A549 or H1975 cells. Alterations in cell proliferation, apoptosis, migration and invasion were analyzed in vitro. A nude mouse tumorigenicity assay was used to test the effect of resistin in vivo. High expression of resistin was predominantly observed in lung adenocarcinoma tissues but not in adjacent normal lung tissues. Resistin expression was significantly associated with increased tumor size, clinical stage as well as lymph node metastasis while negatively associated with progression-free survival (PFS) and overall survival (OS). Expression of resistin was an independent risk factor for PFS and OS. Overexpression of resistin promoted significant proliferation, migration and invasion, while also inhibited apoptosis in vitro. Resistin also promoted tumor formation in nude mice. The potential molecular mechanism was also investigated by in vitro experiments. In conclusion, the present study revealed that a high level of resistin expression in lung adenocarcinoma tissues is associated with poor clinicopathological status and survival. Resistin, which promotes the development of lung adenocarcinoma in vitro and in vivo may be a novel target for lung adenocarcinoma.