Ambrose, has put pen to paper on a three-year deal while Westwood has signed a two-year contract with the Bears.
In addition, second XI skipper Ateeq Javid has also signed a two-year contract.
Ambrose, 29, scored 623 championship runs at an average of 44.5 in 2012 as well as taking 42 catches and a stumping.
The former England keeper, who played in 11 Tests, joined the Bears from Sussex in 2006.
Westwood, 30, a product of the club's development programme, recorded 771 runs at an average of 42.83 last season, including two hundreds, in helping Warwickshire to the title.
Warwickshire assistant coach Dougie Brown said: "Tim and Ian have been key members of the senior squad for several years.
"They both played a major role in last season's championship win, and to secure their futures here at Edgbaston is a great boost for the club."
Javid captained Warwickshire to the County Second XI Championship in 2011 and has made eight first class and three list A appearances to date.