MicroRNAs (miRNAs) are critical translational regulators that act as oncogenes or tumor-suppressor genes. qRT-PCR assay results showed that the expression levels of miR-125a-5p are lower in lung adenocarcinoma (AD) tissues than expression levels in adjacent non-neoplastic tissues. This relative expression was found to be significantly associated with lymph node metastases. Cell growth, apoptosis, caspase activity and Transwell invasion assay results showed that in two lung adenocarcinoma cell lines transfected with a miR-125a-5p mimic, proliferation and invasion rates were found to be significantly reduced, whereas the apoptosis rate of the miR-125a-5p mimic group was enhanced. Subsequent western blotting and luciferase reporter assays showed that miR-125a-5p is able to bind to putative binding sites within the mRNA 3' untranslated region (UTR) of neural precursor cell expressed, developmentally downregulated 9 (NEDD9). Our findings suggest that miR-125a-5p may serve as a therapeutic agent for lung adenocarcinoma through its major target, NEDD9.