Walker was the XFL's leading passer and front-runner for the MVP award with the Houston Roughnecks before the season was canceled.
The Indianapolis Colts signed the dual-threat passer as an undrafted free agent in 2017. He spent parts of two years with the franchise before joining the XFL.
Walker is set to reunite with Panthers head coach Matt Rhule. He was Rhule's quarterback with Temple from 2013 to 2016.
Carolina's quarterback room will look significantly different in 2020 under Rhule. Longtime starter Cam Newton is expected to be traded or released after the team signed Teddy Bridgewater. 2019 third-round pick Will Grier rounds out the group.
Walker threw for 1,338 yards, 15 touchdowns, and four interceptions across five starts for the Roughnecks, earning a 5-0 record.