Wisconsin troops primarily will help in support roles, meaning administrative and logistical duties. Exact missions won't be known until they arrive in Arizona.
"The guard is helping to take on some of those roles which frees up some of the law enforcement officials to conduct actual border operations," said Capt. Joe Trovato with the Wisconsin National Guard.
In April, President Donald Trump directed the Department of Defense to assist federal authorities in securing the border.
National Guard units from border states like California and Arizona mobilized in response, but now they are asking for help.
"The whole purpose of the mission is to assist the Arizona National Guard which is in the process of assisting U.S. Customs and Border Patrol," said Trovato.
Voces de la Frontera, a local immigrant advocacy group, is criticizing Walker's decision, because of the Trump administration's policy of separating families who cross the border illegally.
In a statement, Executive Director Christine Neumann-Ortiz said "We call on Governor Walker to immediately recall our National Guard troops back to their homes in Wisconsin, and to stop aiding Donald Trump's cruel war on immigrant families."
"In our discussions with Arizona, we're not expecting any Wisconsin National Guard troops will physically be on the border," said Trovato. "My understanding is that no Wisconsin National Guard troops will be actually interacting with anybody on the border."
Additional Wisconsin troops could deploy in the coming months, and they are funded to stay in Arizona through September.
About 1,000 Wisconsin National Guard troops deployed in a similar manner in 2006 under the direction of George W. Bush.
The entire Wisconsin National Guard also went to the U.S.-Mexico border in 1916 to assist with a crisis in that era.
Walker reiterated the role of Wisconsin troops in a news conference Monday night, but said the Trump administration policy is a federal issue.
"At least the initial reaction, the guard has been called up to is administrative assistance in terms of the Arizona National Guard," he said. "So in terms of the other policy, we don't have a say in that one way or the other."