The Madden–Julian Oscillation (MJO) is a tropical quasi-periodic (30–90 days) oscillation phenomenon characterized by the slow eastward propagation of the coupled convection-circulation system from the western Indian Ocean to the Western Pacific. The MJO significantly regulates global circulation and weather through exciting Rossby waves that propagate into mid-to-high latitudes. Moreover, the MJO plays an important role in the occurrence of sudden stratospheric warming (SSW) events, suggesting possible extratropical impacts of MJO via a stratospheric pathway. Here, we observe a significant intensification of the time-lagged relationship between MJO phase 7 (P7) and SSW events in recent two decades. The Arctic stratospheric response to P7 is weak during the 1980–1999 epoch but greatly amplified during 2000–2020. Further analysis suggests that the extended persistence of enhanced MJO convection over the equatorial central Pacific, as well as the variation in extratropical basic state, may have contributed to the amplified circulation response to P7 over the North Pacific and downstream regions. These circulation anomalies facilitate the intensification of tropospheric planetary waves, which propagate upward and strongly perturb the stratospheric polar vortex. Our findings may have implications for the predictability of SSW events and mid-latitude weather forecasts over timescales of weeks to months.