The parade kicks off Tuesday morning at the Hynes Convention Center. It will rumble roughly 2 miles (3 kilometres) past the Boston Common and other landmarks before ending at City Hall.
As is tradition, the team will ride through downtown on World War II-era amphibious “duck boat” vehicles.
Officials anticipate more than 1 million attendees, and early trains and subways were jammed. Weather is expected to be unseasonably warm with temperatures above 50 degrees Fahrenheit (10 degrees Celsius).
Mayor Marty Walsh warns fans not to throw anything. Errant beer cans slightly damaged the Red Sox World Series trophy last year.
The Patriots defeated the Los Angeles Rams on Sunday at Super Bowl 53.