Abstract ENSO teleconnections are a key source of Antarctic sea‐ice predictability, particularly in the Antarctic Dipole (ADP) region, but whether this predictability remains stable under the recent transition toward Central Pacific (CP) El Niño is unclear. Here, using a Markov model, we reveal an 83% decrease in sea ice concentration (SIC) predictability, measured by the anomaly correlation coefficient (ACC), during austral winter and spring since 2002. We show that this decline is linked to a weakened ENSO–Antarctic teleconnection, in which the CP El Niño‐triggered Rossby wave train shifts northward away from the Antarctic sea‐ice zone and toward the open ocean. This northward shift reduces the wave train’s influence on Antarctic sea ice, dampens sea‐ice persistence, lowers its signal‐to‐noise ratio, and consequently limits predictability. Our results suggest that ENSO–Antarctic teleconnections may provide a useful benchmark for evaluating and improving Antarctic sea‐ice prediction models.