The right-back has committed his future to the Foxes until 2019 after helping them win a shock title by 10 points last season
Simpson is the second Leicester player to sign fresh terms this week after Marc Albrighton agreed to stay at the club until 2020.
Simpson said: "I'm over the moon
I've been here two years now and the club is going places, I've said all last season.
"The group that we've got here is so close and the manager since he's come has helped me so much and still is helping me improve as a player.
"It's not just the players and coaches, but the whole club
Everyone is just so close and it's a special feeling
I'm happy that I'm staying here for another three years.
"I came here two years ago and it's always difficult coming to a new club
It took me a while to get my debut and get a few games but that was just because of the competition
I managed to get a run of a few games and the end of that first season, we survived.
"I think that helped us a lot for the next season, because we knew what it meant to play in the Premier League
A new manager, Claudio (Ranieri), came in and you obviously don't know whether you're going to be playing
I was given the chance to play and perform and I felt I did that."
Simpson joined Leicester from QPR in 2014 and has made 52 appearances for the Foxes, including playing in 31 of their 38 league games last season.
Boss Ranieri has also signed a new deal this summer along with Jamie Vardy, Riyad Mahrez, Wes Morgan, Ben Chilwell, Kasper Schmeichel and Danny Drinkwater.
Leicester broke their transfer record for the second time this summer to sign Sporting Lisbon striker Islam Slimani on deadline day but despite the big spending and being champions, Simpson insisted the squad has not changed.
He added: "We're loving every second of it and just enjoying it and even though we are the champions, it's not changed anything in the dressing room and at the training ground."
Source : PA
Source: PA