A sediment accretion and carbon accumulation study was carried out in Kamora Estuary, Mimika Regency, Papua Province, Indonesia, to determine the accretion rate and total organic carbon loading in the area as well their correlation with geographical setting and mangrove aerial root type. The sediment stake method was used to measure the elevation changes, whereas the sediment trap method was used to determine sediment accretion and total organic carbon accumulation. Three locations were selected, namely at upstream, middle and downstream the mangrove communities, with each location installed up to 500 m perpendicular to the riverbank. The elevation changes based on sediment stakes were 8.4–12.3 mm year-1. Sediment accretion based on sediment traps was 18.5–25.4 mm year-1 or 1.88–2.98 g cm-2 year-1, while the mean total organic carbon accumulation was 736.8 ±169 g m-2 year-1. The results are higher than those of similar studies in other regions, but they are consistent with other studies in Papua New Guinea. This study found that higher sediment accretion occurred at the riverbank compared with the interior area, while the elevation changes were greater in the upstream area. Higher relative density and higher basal area had a negative correlation with sediment accretion, but the number of roots had a positive correlation with sedimentation. The high sedimentation in the Kamora Estuary is resulting in the expansion of the mangrove forest at a rate of 3% year-1. Assisted mangrove colonization can be applied to expand the mangrove forest, especially considering the use of Rhizophora species, which this study found to be more effective at trapping sediment.