The aim of this study is to evaluate the effects of a 2-month aerobic exercise training programme on C-reactive protein (CRP) levels in non-obese patients with obstructive sleep apnoea. Twenty non-obese and sedentary adult male volunteers underwent polysomnography (PSG) to assess their sleep parameters. After the PSG analysis, the subjects were divided into two groups (CTRL, control and OSA, obstructive sleep apnoea). Twenty-four sessions of aerobic exercise were performed, and PSG was repeated on the night that followed the last physical training session (24th). Blood samples were collected for CRP analysis before the first exercise session and after the last session. The OSA group demonstrated a reduction in sleep latency (SL) after 2 months of physical exercise, and 80% of them showed a lower apnoea-hypopnoea index (AHI), although this difference was not statistically significant. The differences between the CRP values for the CTRL and OSA groups were also not statistically significant at baseline or after 2 months of physical exercise. Furthermore, there was no correlation between the CRP levels and body mass index (BMI) in the two groups assessed. Our results suggest that in non-obese patients with OSA, CRP levels were normal and did not change after 2 months of aerobic exercise training.