Ivar first appeared in WWE on Velocity on December 16, 2005, losing to Doug Basham. The following year, on September 15, 2006, he appeared on SmackDown as Todd Hansen in a losing effort to Sylvester Terkay.
On January 16, 2018, WWE announced that Ivar, as Hanson, had signed a contract with the company and would be reporting to the WWE Performance Center. On March 17, 2018, Hanson and tag team partner, Rowe, made their NXT debut at a house show, defeating the team of Adrian Jaoude and Cezar Bononi in their first match. On the April 11, 2018 edition of NXT, he and Rowe, dubbed War Machine, made their TV debuts, attacking Heavy Machinery (Otis Dozovic and Tucker Knight) and the team of Riddick Moss and Tino Sabbatelli. Two days later on the April 13, 2018 edition of NXT they went on to defeat the team of Danny Burch and Oney Lorcan.
Throughout the beginning of the year, the team of Hanson and Rowe, now dubbed the War Raiders, would continue their winning streak, by defeating several tag teams in the NXT division, including The Mighty and Heavy Machinery. At NXT TakeOver: WarGames in Los Angeles, War Raiders would team up with Ricochet and Pete Dunne in the main event to defeat The Undisputed Era in the eponymous WarGames match. At NXT TakeOver: Phoenix, War Raiders would defeat the team of Kyle O'Reilly and Roderick Strong to win the NXT Tag Team Championship. On April 15, 2019, they debuted on Raw, winning on their debut. On the October 14 episode of Raw, they would capture the Raw Tag Team Championships by defeating the team of Dolph Ziggler and Robert Roode. They would then drop the titles to the team of Seth Rollins and Buddy Murphy on the January 20, 2020 episode of Monday Night Raw, after their reign lasted for 98 days.
On September 7, 2020, on Raw, The Viking Raiders teamed up with Apollo Crews and Ricochet in an eight-man tag team match against The Hurt Business in a losing effort, where Cedric Alexander scored the pinfall over Ricochet.The match was forced to an abrupt ending due to Ivar suffering a legitimate cervical injury during the match.
Ivar would return to action on the April 12, 2021 edition of Raw, teaming up with Erik against Shelton Benjamin and Cedric Alexander in a winning effort.
As part of the 2021 Draft, both Ivar and Erik were drafted to the SmackDown brand. On February 19, 2022, at the Elimination Chamber event, they were attacked by The Usos before their match for the WWE SmackDown Tag Team Championship, but on the March 4 episode of SmackDown, they unsuccessfully challenged the Usos for the titles. On the June 24 episode of SmackDown, the Viking Raiders would return with new gear and face paint, and would violently attack The New Day and Shanky, thus turning heel for the first time since 2018. As part of the 2023 WWE Draft, both Erik and Ivar were drafted to the Raw brand. In October 2023, it was announced that Erik was injured. After a year-long hiatus, Erik returned from injury alongside Ivar on the October 14, 2024 episode of Raw, where they defeated Alpha Academy while reverting back to their War Raiders name and gimmick. Two weeks later, they defeated the LWO and The New Day in a triple threat tag team match to become number one contenders to the World Tag Team Championships held by The Judgment Day's Finn Bálor and JD McDonagh. On the November 25 episode of Raw, they failed to win the titles from Bálor and McDonagh after interference from Dominik Mysterio and Carlito.