The Red Devils were in the market for a new addition following the departure of Graeme Jones.
A man who has worked alongside Martinez throughout his managerial career has returned to club football as deputy to Darren Moore at West Brom.
Jones has been replaced as number two within the Belgium set-up by Thierry Henry.
The Arsenal legend, who linked up with Martinez in August 2016, remains part of the fold after turning down the chance to move into management at Ligue 1 side Bordeaux.
His promotion has allowed Maloney to be brought in by Belgium, with the 35-year-old a man Martinez knows well.
The Spaniard signed the Scot during his time in charge of Wigan, with the pair spending two years together at the DW Stadium.
Maloney, since hanging up his boots in the summer of 2017, has been cutting his coaching teeth within the academy set-up at Celtic.
Martinez is delighted to have welcomed a familiar face on board, telling reporters at the announcement of his squad for upcoming fixtures against Scotland and Iceland: “Graeme Jones did a fantastic job as assistant coach. We wish him all the best.
“We are delighted that Thierry Henry has decided to carry on and stay with the team. He will now work on a full-time basis for Belgium.
“Shaun Maloney is a football player that I worked with. He knows the way we work and is someone who has an exciting coaching career in front of him.”
Belgium are set to face Scotland in an international friendly contest on September 7 before opening their UEFA Nations League campaign against Iceland on September 11.
Martinez added on the challenges which lie ahead for a team which finished third at World Cup 2018: “The Nations League brings a real meaning to the games we will play.
“This is a new and different format that is going to be successful.”