Total humic acids (THA) content in the sediments of six mangroves located north of Cochin in Kerala along the southwest coast of India during the pre monsoon, monsoon and post monsoon period of 2002 is described in relation to the type of vegetation cover in the area. Annual mean values of THA in the sediments ranged from 1.97 to 5.81 pg/g. Monsoon and post monsoon seasons accounted for higher levels of THA in sediments. Litterfall from Rhizophora spp. contributed more THA (214%) to the sediment than that of Avicennia and other types of mangrove plants. Sediment from within the mangrove patches contained 17- 240% higher THA than the adjacent upstream and downstream areas.