In this study, mass concentrations and chemical compositions of PM2.5, including water-soluble ions and elements were determined at the 1,100 m-highland of Mt. Hallasan in Jeju Island across four seasons from August 2013 to August 2014. The average mass concentration of PM2.5 was 12.5±8.41 /m3 with 45.8% of the contribution from eight water-soluble ionic species. Three ionic species (SO4 2-, NH4 +, and NO3 -) comprised 96.2% of the total concentration of ions contained in PM2.5 and were the dominant ions, accounting for 43.5% of the PM2.5 mass at Mt. Hallasan. On the basis of the mass concentration level, seasonal variation, enrichment factor, and relationship among elements, we can presume that Mg, K, Ca, Mn, Fe, Co, Sr, Ba, Nd, and Dy originated mainly from crust or soil and that V, Cr, Ni, Cu, Zn, As, Cd, and Pb were significantly enriched in PM2.5 owing to the effects of the anthropogenic emissions. These results and the local distribution of emission sources and topographic characteristics near this sampling site suggest that the compositions of PM2.5 collected at the 1100 m-highland of Mt. Hallasan were largely influenced by inflow from outside of Jeju Island.