Our findings here demonstrate that, even though the exercise training was not able to alter the collagen deposition in the parenchyma or even some key pulmonary mechanic parameters, the aerobic exercise training putatively reduced the recruitment of immune system cells, the release of proinflammatory mediators/cytokines both in the lung and blood, and increased the IL-10 expression by lung macrophages of mice submitted to an experimental model of bleomycin-induced lung fibrosis. Here, IL10 is linked to pulmonary fibrosis.