McArthur has signed a four-year deal at Wigan after passing a medical.
“James is a really exciting prospect and we are all delighted that he has chosen to join Wigan Athletic,” Martinez told the club’s official website.
“We are building a squad here at the DW and I see James as being another real quality addition who will add great competition in the midfield areas.
“He is young, hungry, desperate to play for us in the Premier League and I believe he has all the attributes you need to be a success at this level.
“We want James to feel at home here, enjoy his football and progress his career as he helps with his daily standards, to make Wigan Athletic a stronger football team.
“James McCarthy adapted to life at Wigan and James McArthur has the potential to be just as impressive.
“James has played a huge amount of games for a player of his age and his desire and winning mentality will be a great asset for our squad.”
