Abstract Analysis of sea surface temperature (SST) data robustly detects dipoleâpattern decadal anomalies in the southern Atlantic and Indian Oceans (SAIOs) that coâoccur like twins, termed the AtlanticâIndian Twin Dipoles (AITDs). The mechanisms governing the AITDs are investigated based on observational data sets, climate model simulations, and ocean model experiments. We show that the AITDs are coupled with alterations in subtropical highs that involve a variety of regional airâsea processes. Specifically, while cloudâcontrolled radiative heating plays key role in the Atlantic, windâdriven turbulent heat flux change is essential in the Indian Ocean. Windâdriven ocean dynamics are also important near the eastern boundaries of the SAIOs. Interdecadal Pacific Oscillation and Southern Annular Mode are conducive to the AITDs by modulating the subtropical highs. Our results highlight the transâbasin linkage between the SAIOs, providing implications for predicting the Southern Hemisphere climate and regional extremes.