We characterized the pattern and magnitude of decadal sea-level variability in the Australasian Mediterranean Sea by using high-resolution ocean models. Our results suggest low-frequency ENSO variations and PDO-related changes as a primary source of variability. Sensitivity experiments indicate that anomalies are primarily driven by wind stress fluctuation but are also amplified by local heat and freshwater fluxes. Intrinsic variability is relevant in the South China Sea.