We present a monthly resolved, 213-year stable isotope time series from a coral from Guam (13°N, 145°E), which is located on the northern edge of the western Pacific warm pool. Oxygen isotopic composition of the coral skeleton (δ 18Ocoral) shows seasonal, interannual, and decadal variability, which documents significant oceanographic changes related to thermal and hydrologic variations in this region. The δ18Ocoral anomaly reflects sea surface temperature (SST) anomaly and sea surface salinity (SSS) anomaly with significant r values of -0.69 and 0.49, respectively, which are strongly linked to oceanographic changes that occur during El Niño-Southern Oscillation (ENSO) warm and cool phases. We identified 46 ENSO warm (El Niño) and 53 cool phases (La Niña) in the coral record, which are consistent with those phases reconstructed by Niño 3.4 SST anomaly. Spectral analyses of the δ 18Ocoral anomaly record for the years 1790-1999 identified significant peaks around ∼3 to ∼7 years. These results indicate that the Guam coral has recorded ENSO periodicity. The δ18Ocoral anomaly shows decadal variability of ∼15- to ∼45-year periodicity with significant shifts (<0.2‰) from warmer to cooler condition and vice versa. An accumulative decrease in δ 18Ocoral time series may imply ∼0.75°C warming of SST and ∼0.23‰ freshening of seawater δ18O, corresponding to a decrease of SSS by ∼0.85, in the northwestern tropical Pacific over the last 2 centuries.