Phosphate amendments have been shown to increase arsenic (As) availability to plants by promoting the desorption of arsenate from soil particles. We hypothesized that the application of phosphorus to As-contaminated substrate would enhance As uptake by shrub willow (Salix spp.) and increase aboveground As accumulation. Two shrub willow clones were grown in pots containing either field-collected As-contaminated soil (55 mg As kg^-1) or potting mix spiked with sodium arsenate (0, 100, and 250 mg As kg^-1) for 16 and 14 weeks, respectively. Pots containing field-collected soil received one of three treatments: no amendment, superphosphate incorporated into soil prior to planting, or liquid sodium phosphate (75 mg L^-1) applied twice after planting. Sodium arsenate-spiked potting mix received either no phosphate amendment or two applications of liquid sodium phosphate periodically during the growth period. Total stem length and aboveground biomass were lower for the potting mix treated with 100 and 250 mg As kg^-1 compared with untreated controls. Phosphate amendment was not significant for these growth indicators. As concentrations ranged from 30 to 100 mg As kg^-1 in leaves of the As-tolerant clone 99202-011 (S. viminalis x miyabeana) and from 10 to 40 mg As kg^-1 in the As-sensitive clone 00X-026-082 (S. eriocephala). Total stem length, aboveground biomass, and leaf area were significantly greater for plants receiving phosphate amendments in the field-collected contaminated soil. Leaf As concentrations were below detection limits for all treatments.