Marine heatwaves are known to cause severe ecosystem damage and therefore have received attention in recent years. However, the focus has tended to be on global (surface) studies, but not coastal waters. Mesoscale eddies are important and underappreciated components in the eddy-dominated western boundary current system, but their roles in driving marine heatwaves in the East Australian Current have largely been unexplored. Here we show that cold cyclonic eddies can modulate the most intense coastal marine heatwaves on record inshore of the East Australian Current. We also show that the anticyclonic eddies can drive ocean warming in the East Australian Current extension regions. Our study has implications for future investigations into eddy-EAC interactions and the evolution of marine heatwaves in other western boundary current regions.