Idiopathic pulmonary fibrosis (IPF) is a progressive, debilitating, and fatal lung disease characterized by interstitial fibrosis with decreasing lung volumes and hypoxemic respiratory failure. The prognosis for patients with IPF is poor and the quest to find effective therapies has been unsuccessful. Despite several clinical trials over the past decade, there are no U.S. Food and Drug Administration-approved treatments for patients with IPF and thus no standard of care. In terms of pathogenesis, IPF is characterized by alveolar epithelial cell injury and activation with interstitial inflammation, fibroblast proliferation with extracellular matrix collagen deposition, and loss of lung function. Because mesenchymal stem cells (MSCs) home to sites of injury, inhibit inflammation, and contribute to epithelial tissue repair, their use has been suggested as a therapy for the treatment of IPF. MSCs have potential as a novel therapeutic agent in multiple diseases and they have been safely administered in a number of clinical trials. Some, but not all, preclinical studies in animal models of lung fibrosis suggest that MSCs might be effective in the treatment of IPF. Given the safety and ease of MSC administration in other patient populations, the results in preclinical animal models of IPF, and the major need for novel therapeutic options in this devastating disease, we propose that carefully designed clinical trials of MSCs for the treatment of patients with IPF are appropriate. Establishing safety in the setting of IPF is the first priority in early clinical trials followed by clinical and biological measures of efficacy.