We analyzed the chemical composition of wood produced by Māmane, a tropical tree growing in Hawai’i, in order to reconstruct changes in climate over the Hawaiian Islands. Specifically, we measured changes in the relative abundance of carbon and oxygen isotopes taken up by the trees during photosynthesis at high elevation sites on Mauna Kea. We found that these isotopes reflect the climatic conditions (precipitation and temperature) under which the trees lived, allowing us to reconstruct relative changes in climate extending back ~130 years. Our results indicate decadal-scale changes in precipitation that correlate well with large-scale atmospheric and ocean circulation patterns that dominate much of the Pacific. In addition, we interpret a general decrease in precipitation since the 1920s that is consistent with rain-gauge measurements. Our long-term climate record also correlates well with measurements showing a decrease in snow cover on Mauna Kea. These results demonstrate how detailed measurements of the wood chemistry of Māmane trees can be used to extend our record of natural climate variability in Hawai’i to a wider geographic extent and across longer time periods than the instrumental record allows. This new climate record produced from Māmane wood has implications for better understanding background, natural climate variability in the Hawaiian Islands and may further help conservation efforts in the fragile upland tropical ecosystem.