Wisconsin is now the seventh state to permit members of the National Guard to carry weapons on duty, following its authorization by Gov. Scott Walker.
The decision follows the attack on two military facilities in Chattanooga, Tennessee last week.
"Allowing our National Guard members to carry weapons while on duty gives them the tools they need to serve and protect our citizens as well as themselves," Walker, a Republican and presidential candidate, said in a statement.
The governors of Arkansas, Florida, Indiana, Louisiana, Oklahoma and Texas, all Republicans, have already announced plans to arm Guardsmen.
Muhammad Youssef Abdulazeez killed four Marines and a sailor last week when he opened fire on a military recruiting station and a Navy and Marines reserve center in Chattanooga.