<p>Marine heatwaves can interact across ocean basins through atmospheric teleconnections, but such inter-basin links remain poorly understood. Here we show that boreal spring and summer marine heatwaves in the Caribbean Sea are significantly connected to marine heatwaves in the Indian Ocean during the preceding winter. Using observational data and climate model simulations, we identify that boreal winter Indian Ocean marine heatwaves trigger atmospheric convection, generating an eastward-propagating Indo-Pacific-Atlantic Rossby wave train. This wave train alters the regional Hadley circulation and renders the overlying atmosphere warm, moist, and stable over the Caribbean Sea, reducing latent heat loss from the ocean, driving sea surface warming and promoting the intensification of marine heatwaves. These findings reveal a robust teleconnection pathway that allows climate signals from one basin to amplify marine heatwaves in another.</p>