Henderson, who spent last season on loan with League One outfit Shrewsbury Town, chose to remain at Old Trafford among interest from various clubs such as Norwich City.
The 21 year-old will remain with the Red Devils until 2020, with the deal including an option for a further year.
The shotstopper, who has risen through the ranks at the club, is honoured to be able to prolongue his time as a Manchester United player.
He told 'MUTV': "I'm really delighted. Coming off the back of last season and playing games at Shrewsbury and having a good season there, to return to the biggest club in the world and put pen-to-paper again is a great achievement for me and my family. It's another dream come true.
”Obviously, there was a lot of interest after last season, when I've done myself well going out and playing but, look, United are the biggest club in the world and have been my club since day one so, of course, they are always first in my mind.
All my family are here with me now and it's an honour. To come from where we started from, from nothing, to come all this way is fantastic and I'm just really delighted.”
14 June 2018