The Courier-Journal reported that Robert and Rosalind Grant and their 23-month-old granddaughter sought medical attention and treatment in May after finding the mouse. The family filed suit in Jefferson Circuit Court on Monday.
Wal-Mart spokesman Phillip Keene said the retail giant takes quality and safety seriously and is looking into the complaint, along with the supplier, Ohio-based Superior Dairy Inc.
The Louisville paper reported that the child had blood in her stool from drinking the tainted milk.
The Grants claim they bought the milk May 1 at Sam's Club, which is owned by Wal-Mart, and the container had not been tampered with.
Attorney William Davis, who represents the family, described his clients as "completely shocked."
Information from: The Courier-Journal,