Pain in the middle of chest when sleeping on the side is mostly considered to be caused by intercostal neuritis, pleurisy, pericarditis, trauma and so on. 1. Intercostal neuritis: Intercostal neuritis may cause chest pain in the middle of the chest when sleeping on the side, this kind of disease will cause pressure pain, sleeping on the side may make the affected area be squeezed, so that the pain symptoms become more obvious, the patient will have burning pain, pins and needles and other adverse symptoms. 2. Pleurisy: patients will have cough, dyspnea and other symptoms, usually there is obvious chest tightness, violent cough or large movements will make the pain worse, tuberculous pleurisy can also be accompanied by low-grade fever, night sweats and other systemic symptoms. 3. Pericarditis: Side sleeping chest pain in the middle of the chest, may also be suffering from pericarditis caused by discomfort, the patient’s heart or around the heart will appear pressure, the onset of cold sweat, panic and other adverse symptoms, may also cause dyspnea. 4. Trauma: local soft tissue injury or rib fracture caused by impact or extrusion, etc., which may be manifested as chest pain, chest tightness, etc., and the pain may be aggravated by side-sleeping pressure on the affected area. There are many reasons that cause chest pain in the middle of the chest when sleeping on the side, and it is recommended that patients go to the hospital in time to avoid delaying the condition.