Biomarkers have the potential to become central to the clinical evaluation and monitoring of patients with chronic fibrosing interstitial lung diseases with a progressive phenotype. Here we summarize the current understanding of putative serum, bronchoalveolar lavage fluid and genetic biomarkers in this setting, according to their hypothesized pathobiologic mechanisms: evidence of epithelial cell dysfunction (eg, Krebs von den Lungen-6 antigen), fibroblast proliferation and extracellular matrix production/turnover (eg, matrix metalloproteinase-1), or immune dysregulation (eg, CC chemokine ligand 18). While most of the available data comes from idiopathic pulmonary fibrosis, the prototypic progressive fibrosing interstitial lung disease, there are data available in the broader patient population of chronic fibrosing interstitial lung diseases. While a number of these biomarkers show promise, none have been validated. In this review article, we assess both the status of proposed biomarkers for chronic fibrosing lung diseases with a progressive phenotype in predicting disease risk or predisposition, diagnosis, prognosis and treatment response, and provide a direct comparison between idiopathic pulmonary fibrosis and other chronic fibrotic interstitial lung diseases. We also reflect on the current clinical usefulness and future direction of research for biomarkers in the setting of chronic fibrosing interstitial lung diseases with a progressive phenotype.