PROBLEM TO BE SOLVED: To provide a granisetron-containing aqueous formulation suitable as a stable premix formulation which is a plastic bag or bottle formulation containing 1 mg of granisetron.SOLUTION: There is provided a granisetron-containing aqueous formulation prepared by storing approximately 50 to approximately 100 mL of an aqueous solution which contains 1 mg of granisetron, a tonicity agent, a buffer and a pH adjusting agent and has a pH of 5.0 to 7.0 in a plastic container made of a material such as polypropylene.