Jones, 30, hasn't been assigned to an XFL team. The former NFL backup will be part of an eight-man quarterback draft that takes place this fall.
"Quarterback Landry Jones, former University of Oklahoma star and quarterback in the National Football League, is the first player to officially sign with the XFL," league commissioner Oliver Luck said in a statement. "Landry typifies the type of player we want. He's an accomplished athlete with a passion for the game.
"Landry is the first of our tier-one quarterbacks to sign. We'll have more news as we lead up to our draft in October with future signings."
The XFL, which is scheduled to debut in February, plans to hold its first draft in October, followed by team minicamps in December and a three-week training camp in January.
Jones started five games in five seasons (2013-17) with the Steelers before spending last season with the Jacksonville Jaguars. He worked out with the Oakland Raiders during OTAs in May but was eventually cut.
During his NFL career, Jones played in 18 games (five starts) and completed 63.9 percent of his passes for 1,310 yards, eight touchdowns and seven interceptions.