We present ~twelve year-long time series of biweekly cave drip water (oxygen isotope) variations from three sites from Gunung Mulu National Park in Northern Sarawak, Borneo. Lastly, seven spatial surveys of stalagmite and non-stalagmite forming cave drip water (oxygen isotopes) were taken in: August 2008 (N = 63), Feb/Mar, 2010 (N = 128), Oct/Nov 2012 (N = 291), Feb/Mar 2013 (N = 37), May, 2016 (N = 92), May, 2017 (N = 180), and Mar/Apr, 2018 (N = 124). Twelve years of monitoring data presented in this study identify individual El Niño-Southern Oscillation (ENSO) events in rainfall and cave drip water isotopic composition, providing a robust interpretive framework for past and future stalagmite isotope records from this site.