The Pro Football Hall of Famer was at his house in Malibu, California, when a 39-year-old woman entered the home through an unlocked door, grabbed the baby and walked into another room. Montana got the child back before the intruder ran away.
The woman was eventually arrested on kidnapping and burglary charges.
Los Angeles County Sheriff's deputies happened to be in the area, allowing someone inside the home to flag them down in time to catch the woman in question.
Montana, 64, is best known for his career with the San Francisco 49ers, leading the squad to four Super Bowl titles. The two-time MVP also spent two years with the Kansas City Chiefs before retiring after the 1994 season.
He was inducted into the Hall of Fame in 2000.