Arsenic contamination of soils occurs from various anthropogenic sources such as pesticides, fertilizers, wood preservatives, cattle dip sites, tannery industries, coal combustion, etc. Being a Group A human carcinogen, arsenic poses a great threat to humans as well as to the environment. Current remediation methods for arsenic-contaminated soils include soil removal and washing, physical stabilization, and/or the use of chemical amendments, all of which are expensive and disruptive to nature. In this study, we evaluated the effectiveness of water treatment residuals (WTRs) in remediating arsenic-contaminated soils. WTRs are waste by-products from municipal water treatment plants, rich in amorphous Al or Fe oxides and hydroxides. WTRs have been used to decrease phosphorus solubility and bioavailability in soils. Since phosphorus and arsenic are both group V elements having similar chemical properties, we assumed that WTRs would be equally effective in decreasing arsenic bioavailability. The objective of this study was to examine the bioavailability of arsenic and phosphorus in soils chemically amended with WTRs at different rates. A laboratory incubation study was conducted using Immokalee series soil (a sandy spodosol from Florida) which was spiked with an arsenical pesticide in the form of sodium arsenate at a rate of 90 mg As/kg and fertilized with triple super phosphate at a rate of 115 mg P/kg. The soil was then amended with 2 WTRs (Al- and Fe-WTRs) at 5 rates ranging from 0 to 5 % (w/w). Bioavailability of arsenic and phosphorus were determined at 0-time (immediately after WTR-amendment), after 6-months and 12-months of equilibration. Results obtained indicate that Fe- and Al-WTRs have the potential to decrease arsenic bioavailability even in the presence of phosphorus, and that decrease in bioavailability is a function of in WTR amendment rates.