Guadagno was a federal prosecutor before she was elected Monmouth County sheriff.
In a video on Christie's networking sites, Guadagno said she's proud to be running for lieutenant governor at a time in New Jersey's history where they'll have to make tough decisions.
Christie and Guadagno plan to make campaign stops in Asbury Park, Woodbridge and Garfield, N.J. Monday.
Gov. Jon Corzine has yet to announce who his running mate will be.