Obstructive sleep apnoea (OSA) constitutes a multisystemic disorder often associated with cardiovascular and metabolic disorders. Thus, far, the underlying pathophysiological processes are not fully understood. In total, 142 plasma samples were acquired: 50 from controls (CON), 45 from mild/moderate OSA (M-OSA) patients, and 47 from severe OSA (S-OSA) patients. Proteomic and metabolic signatures significantly differed among S-OSA, M-OSA, and CON samples. A novel plasma biomarker panel including two proteins (ACTR2 and ENO1) and three metabolites (2-aminobicyclo[2 2·1], heptane-2-carboxylic acid, 1-O-[2r-hydroxy-hexadecyl]-sn-glycerol, and 1-pentadecene) was developed to identify S-OSA (AUC: 1.000) and distinguish severe cases from nonsevere cases (AUC: 0.813). An independent cohort was used to validate the model by distinguishing S-OSA samples from M-OSA (AUC: 0.729) and CON (AUC: 0.990) samples. Glycolysis pathway activation was identified as a characteristic of OSA; it may contribute to diabetes mellitus onset in OSA patients. Dyslipidaemia, foamy macrophage formation, platelet activation, and actin cytoskeleton might collectively play a key role in vascular damage in OSA patients, contributing to the development of atherosclerosis. These findings reveal molecular bases for OSA-related cardiometabolic complications and provide new diagnostic biomarkers for OSA and the identification of severe cases.