The Dutchman helped United get into the festive spirit by lighting up the tree, which will remain at the Theatre of Dreams for the whole festive period.
Also in attendance at the event were staff from the club and children who attend projects hosted by the Manchester United Foundation.
Van Gaal will turn his attentions back to the Premier League this weekend when his side host Hull City at Old Trafford on Saturday afternoon.
The Red Devils are looking to build on their 2-1 victory over Arsenal at Emirates Stadium last weekend.
The win at Emirates Stadium hoisted Van Gaal’s side up to fourth place in the Premier League table.
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