This dataset includes geochemical and densitometric data from an early Little Ice Age (LIA; 1273–1332±4 CE) Porites microatoll slab collected in November 2017 from Arno Atoll, Marshall Islands. 230Th-U-dating was performed at GEOMAR, Kiel, Germany. Powder samples were extracted along the growth axes of the coral at 1 mm resolution (9.5 samples per annual band). Trace elements were measured using an Agilent 720 (axial) inductively coupled plasma optical emission spectrometer at MARUM, University of Bremen, Germany. Mean Sr/Ca of JCp-1 standards measured along with this coral was 8.914±0.012 mmol mol-1 (n = 11; 1 sd). Stable isotopes were measured using a Finnigan MAT 252 mass spectrometer equipped with an automated Kiel III carbonate preparation device at the Stable Isotope Laboratory of MARUM, Bremen, Germany. Skeletal density was measured using a γ-densitometer at the Goethe University, Frankfurt am Main, Germany. The age chronology is based on coral Sr/Ca using one tie point each annual cycle for the summer SST peak (minimum in Sr/Ca) in September/October. Subsequently, the time series of geochemical and skeletal density data were linearly interpolated to an evenly spaced time series with bimonthly resolution (6 samples year-1).