The magic circle firm is advising JPMorgan, the investment bank that provided the £300m debt used by the owner of the Tampa Bay Buccaneers to finance his controversial offer.
It is understood that Shearman landed a role acting for the investors holding preferred securities.
The conclusion to Glazer's protracted battle for the club came about last Thursday (12 May), after the US sports tycoon persuaded JP McManus and John Magnier, the Irish horseracing millionaires, to sell their 29 per cent stake in the Premiership club.
Manchester United's board had resisted Glazer's bid as it believed it was over-leveraged.
Commenting on Glazer's success, a source close to the billionaire said: "It's pretty unusual for a hostile mandatory offer to go unconditional straight away. Glazer's stake went from just over 50 per cent to over 70 per cent in just three hours."
Meanwhile, a source close to Manchester United said: "In many ways it was an inevitable result. It was a very sad day."