This study compares the organic chemistry of peat beneath one of last remaining pristine tropical peat forests in Southeast Asia with a neighbouring peat dome that has been deforested, but not intentionally drained, in the Belait district of Brunei Darussalam, Borneo. We characterized the solid and dissolved organic matter collected from the two domes, through a combination of methods including elemental analysis, phenolic content and Fourier transform infrared spectroscopy (FTIR) investigation of solid peat, as well as optical characterisation (absorbance, fluorescence) of dissolved organic matter (DOM). The peat had a high content of lignin, consistent with its origin from the Shorea albida trees on the domes. Dissolved organic carbon (DOC) concentration in the pore water was significantly greater in the deforested site (79.9 ± 5.5 mg l -1 ) than the pristine site (62.2 ± 2.2 mg l -1