Keith Smart, who coached the Golden State Warriors last season, signed a two-year deal with the Kings.
Next season's salary is not guaranteed, giving the Kings an opportunity to pursue another coach if the team makes little or no progress under Smart.
The decision to fire Westphal ended a disappointing start to the 2011-12 season. All five of the Kings' losses this season are by double digits.
Westphal was in his third season and had a 51-120 record.