Curcumin is a natural bioactive material which has very low water solubility. In this work, solubility of curcumin was increased with a natural edible linear polysaccharide, alginate, in ultrasound medium at 25oC. Curcumin solubility in alginate-water solution (2% by weight) was increased up to 1.525 ×10-3 M at pH 7 and up to 0.317 ×10-3 M at pH 2.4. The critical aggregate concentration of alginate for curcumin-alginate complexes, were determined as 1 % (by weight). The sizes and surface charges of curcumin-alginate complexes were measured. Nano sized complexes with a uniform size distribution were obtained. Antioxidant capacities of the complexes were determined by 2, 2-Diphenyl-1-picrylhydrazyl and Folin- Ciocalteu methods. For both methods, the antioxidant capacities of complexes were higher than that of curcumin itself. Complexes were stable at all dilutions with water and can be considered as candidate materials for food and drug preparations.