Seafarers are exposed to a greater risk of illness, injury, or death than onshore workers. They are also, deprived of the professional medical care and assistance provided for workers inshore. Medical evacuations are crucial for saving the lives of onboard seafarers. We, therefore, investigated the relationship between seafarer demographics, ship features, incident characteristics, and medical evacuation. The study included a total of 4668 contacts related to seafarers from merchant cargo ships to the Telemedical Assistance Service (TMAS) of Turkey, of which 471 incidents required a medical evacuation at sea. The Classification and Regression Tree (CART) approach and logistic regression were employed to analyse the medical evacuation cases. The most significant explanatory variable determining medical evacuation cases was ship location (Wald = 285.45, p = 0.00) while ship flag, ship age, ship type, seafarer age, working site of seafarer, and seafarer nationality were also statistically significant factors (p < 0.05). This study thus provides information on the factors affecting evacuations at sea. Understanding the risk factors leading to evacuations will ensure that appropriate measures are taken to prevent serious incidents and, timely evacuation decisions are made to save lives on board.