The 35-year-old is available on a free transfer this summer, having seen his contract with Leicester City expire at the end of June, and he is currently considering his options for the 2023-24 campaign.
Evans has been training with Man United over the last week or so, with the Northern Ireland international back at the club that he represented on 198 occasions between 2006 and 2015.
The centre-back won three Premier League titles, the Champions League, two League Cups, four Community Shields and the Club World Cup during his time at Old Trafford.
Man United have now announced that Evans has penned a short-term deal with the Red Devils, allowing him to feature in their upcoming pre-season games in Edinburgh and San Diego.
"The Academy graduate had been training with the Under-21s whilst considering his options, following his departure from Leicester City at the end of last season," read a statement on Man United's official website.
"As part of the Academy training programme, he has also taken part in a number of first-team sessions and impressed Erik ten Hag and the coaching staff."
Evans will therefore be a part of the group that faces Lyon in Edinburgh on Wednesday before travelling to the United States for the club's pre-season tour, and he will be involved for the academy against Wrexham on July 25, while the first team are in Houston to tackle Real Madrid.
The club's plans for the defender after the two matches are unclear, although there could be a spot open in the squad if Harry Maguire departs in the coming weeks.
Evans left Man United for West Bromwich Albion in 2015, spending three years with the Baggies ahead of a switch to Leicester in the summer of 2018.
The defender enjoyed a successful spell with Leicester, featuring on 152 occasions in all competitions, scoring seven goals and registering five assists in the process.
However, an injury-hit 2022-23 campaign saw Evans only make 14 appearances, and he left the Foxes following their relegation to the second tier of English football.
Man United have already released central defenders Phil Jones and Axel Tuanzebe this summer, while Eric Bailly is also widely expected to depart on a permanent basis in the coming weeks.