Walsh missed another extra point in a loss to the Washington Redskins on Sunday.
Forbath was one of six kickers who worked out with the Vikings last week, a group that also included veterans Zach Hocker, Travis Coons, and Randy Bullock, as well as rookies Marshall Koehn and Aldrick Rosas.
The 29-year-old Forbath signed with the New Orleans Saints last season after appearing in one game for the Washington Redskins, and finished a 10-for-15 on field goals and 34-for-35 on extra points through 11 games.
Forbath has a career-long of 57 yards, and is 124-for-127 on extra points in his career.
The move reunites Forbath with a pair of former UCLA teammates: punter Jeff Locke and long snapper Kevin McDermott.
Forbath and Locke played together for two seasons from 2009-10, while McDermott snapped for UCLA in 2011.