Understanding the response of the El Niño-Southern Oscillation (ENSO) to global warming requires quantitative data on ENSO under different climate regimes. Here, we present a reconstruction of ENSO in the eastern tropical Pacific spanning the last 10 thousand years (ka) derived from oxygen isotopes in fossil mollusk shells from Peru. We find that ENSO variance was close to the modern level in the early Holocene and severely damped ~4-5 ka. In addition, ENSO variability was skewed toward cold events along coastal Peru 6.7-7.5 ka owing to a shift of warm anomalies toward the Central Pacific.