Arsenic (As) is one of dangerous heavy metals which is toxic if it was accumulated by living organism and it is difficult to degrade in the environment. This research was conducted to determine the contamination level of As present in the sediment fraction, the effect of pH on the extraction process and the bioaccumulation of As by carp (Cyprinus carpio L.). The sediment sampling was conducted at three stations in Jakarta Bay waters. The fractionation test was based on TCLP (Toxicity Characteristic Leaching Procedure). Bioaccumulation experiment was done for 28 days by giving As as a single-As and metals mixture with As in the seawater. Sediment and biota samples were analyzed by AAS. The results showed that the concentration of As in sediment was 1.008-1.552 μg/g. Based on the Dutch Quality Standards for Metals in Sediments, the tolerable concentration of As is 29 μg/g. The concentrations of arsenic by the fractionation of pH 3, 5, and 7 were 0.049-0.058 μg/g, 0.077-0.091 μg/g, and 0.045-0.069 μg/g, respectively. The concentration of a single-As accumulated by Cyprinus carpio L. in gills and flesh were 0.177 μg/g and 0.166 μg/g respectively, while as metals mixture with As were 0,166 μg/g and 0,162 μg/g respectively.