Pulmonary fibrosis, particularly idiopathic pulmonary fibrosis, represents a chronic and progressive disease with high mortality and limited therapeutic options. Excessive deposition of extracellular matrix proteins results in fibrotic remodeling, alveolar destruction and irreversible loss of lung function. Both innate and adaptive immune mechanisms contribute to fibrogenesis at several cellular and non-cellular levels. Here, we summarize and discuss the role of immune cells (T cells, neutrophils, macrophages and fibrocytes) and soluble mediators (cytokines and chemokines) involved in pulmonary fibrosis, pointing towards novel immune-based therapeutic strategies in the field.