The problem of the present invention is to provide a method for preserving mammalian cells over a long period of time using a solution for cell transplantation, capable of effectively suppressing cell death when the mammalian cells have been preserved, and the solution for cell transplantation. The present invention is characterized in that mammalian cells are preserved in a physiological aqueous solution for cell transplantation, comprising 2.0 to 6.0% (w/v) of trehalose, a derivative thereof, or a salt of trehalose or the derivative (a trehalose) and 4.0 to 7.0% (w/v) of dextran, a derivative thereof, or a salt of dextran or the derivative (a dextran). The effects of a trehalose and a dextran contained in the physiological aqueous solution for cell transplantation can suppress a decrease in the cell survival rate when mammalian cells are preserved for a long period of time (at least 14 days). The physiological aqueous solution is preferably one selected from the group consisting of lactate Ringer's solution, saline, Ringer's solution, and acetate Ringer's solution； particularly preferred is lactate Ringer's solution or saline.
