Oil palm plantation is the most common agricultural land use on peatlands in South East Asia. However, the carbon (C) balance of oil palm plantation on peat soil is not well understood. Field studies on net primary production (NPP) of oil palm plantations on peat are scarce. Therefore, we assessed the above-ground and below-ground NPP in two different mature oil palm plantations established on peat. One was an industrial plantation in Riau Province and the other was a smallholder plantation in Jambi Province, Indonesia. Above-ground NPP (ANPP) was calculated from the production of the tree canopy, pruned fronds, fruit bunches and understorey vegetation, whereas below-ground NPP (BNPP) included the production of coarse roots (with trunk bases) and fine roots. Annual total NPP (ANPP + BNPP, as C) was estimated to be 17.3 Mg ha?1 yr?1 in the industrial plantation and 13.5 Mg ha?1 yr?1 in the smallholder plantation. The NPP was dominated by ANPP, which accounted for 81 % and 73 % of NPP in the industrial and smallholder plantations, respectively.