Megakaryocytes (MKs) are typical cellular components in the circulating blood flowing from the heart into the lungs. Physiologically, MKs function as an important regulator of platelet production and immunoregulation. However, dysfunction in MKs is considered a trigger in various diseases. It has been described that the lung is an important site of platelet biogenesis from extramedullary MKs, which may play an essential role in various pulmonary diseases. With detailed studies, there are different degrees of numerical changes of MKs in coronavirus disease 2019 (COVID-19), acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), lung cancer, pulmonary fibrosis (PF), and other pulmonary diseases. Also, MKs inhibit or promote the development of pulmonary diseases through various pathways. Here, we summarize the current knowledge of MKs in pulmonary diseases, highlighting the physiological functions and integrated molecular mechanisms. We aim to shine new light on not only the subsequent study of MKs but also the diagnosis and treatment of pulmonary diseases.