McNair made 27 appearances for the Red Devils following his 2014 debut under Louis van Gaal, including 24 outings in the Premier League.
He emerged from the Red Devils’ academy ranks as a midfielder but was utilised as a centre-back by the Dutchman and that versatility has increased the 21-year-old’s appeal.
Love, meanwhile, made just one appearance for United in the Premier League but arrives at the Stadium of Light highly-rated, having represented Scotland eight times at youth level.
Earlier this week, The Daily Mail revealed that Jose Mourinho had offered the pair to the Wearside club and the situation has developed rapidly since then, with the Black Cats agreeing a combined transfer fee on Wednesday.
Sunderland have now announced their arrivals via the club’s official website, also confirming that the double deal is worth £5.5million. Both have signed four-year contracts.