MicroRNAs (miRNAs) are emerging as important modulators in cellular pathways and they appear to play a key role in tumorigenesis. MiR-145 is downregulated in several human malignancies, including lung cancer, but the responsible molecular mechanisms remain unclear. We previously reported that restoration of hsa-miR-145 inhibits cancer cell growth in lung adenocarcinoma patients with epidermal growth factor receptor (EGFR) mutation. This study showed that hsa-miR-145 targets EGFR and nucleoside diphosphate linked moiety X-type motif 1 (NUDT1 or MTH1) in lung adenocarinoma cells. The mRNA expressions of EGFR and NUDT1 were significantly downregulated after miR-145 transfection in human lung adenocarcinoma cells. Our results demonstrated miR-145 in the negative regulation of EGFR and NUDT1 expressions at both mRNA and protein levels. Further analysis showed that miR-145 has the ability to inhibit cell proliferation on transfected lung adenocarcinoma cells over three time points (24, 48 and 72 hours). Upregulation of miR-145 appeared to be an important gene regulation mechanism for the proliferation of lung adenocarcinoma cells and it correlated strongly with the downregulation of EGFR and NUDT1. Interestingly, our study revealed that the altered proliferation in lung cancer cells is not accompanied by changes in apoptosis. Our findings provided new insight into the complex regulating pathway comprising of miR-145, EGFR, NUDT1 and other unknown factors which function in cell proliferation but not in apoptosis. Understanding miR-145's targets and its regulating pathways may lead to new therapeutic strategies for lung adenocarcinoma.