The 32-year-old’s previous contract was due to run out at the end of the season and he would have been able to start negotiating with other clubs in the winter transfer window.
Evans has made 89 appearances for Brendan Rodgers’ men since joining from West Bromwich Albion in the summer of 2018.
He was instrumental in the Foxes qualifying for the Europa League last season.
"It is a club that I didn't want to leave. I've enjoyed my time and I'm delighted to extend the deal," Evans told BBC Sport Northern Ireland.
"From the moment, I came into the club, I could see that they set really high standards."
"There's the investment that they have put into the club in terms of the training ground and there are plans in the future to redevelop the stadium as well.
"There's also always investment going into the playing squad which is huge and we've got a great manager in charge at the moment.
"Anyone who plays under Brendan would say that. He likes his players to express themselves. He gives them lots of confidence and I feel like I've benefited from that style of football."
Evans has made 15 appearances in all competitions for Leicester this season.
