The 22-year-old has impressed while filling in for the injured Rio Ferdinand in a number of games this season.
“Jonny has signed a new deal,” confirmed manager Sir Alex Ferguson.
“We have been working on it for a few months now and I am happy that he has signed it.
“Jonny Evans has played a lot of football this year.
“For a centre-half at 22 years of age to play so many games and show the quality he has, is tremendous.”
