The former England Under-20 international, who has made 116 appearances for the cub, has been branded "an outstanding scrum-half" by head coach Richard Hill.
Arr told the club's official website: "I'm delighted to sign and extend my career at Warriors. I truly feel we are on the verge of moving on and it does feel like something is happening now at Warriors that can make a difference.
"I've seen a lot of things change here for the better during my time here and this season we have been competitive in every game we have played. I don't feel we are far away from breaking the mould here."
Meanwhile Hill added: "Jonny is an outstanding scrum-half. He is technically very good in terms of his passing, kicking and defence. He plays a quick game which suits our attacking game.
"He has really come back into the selection frame as our attacking playing style has evolved. He gets the ball away from the breakdown quickly and so has come into his own.
"Jonny's way of playing really suits the multi-phase and fast game we want to play and I'm sure his strengths will continue to be a huge asset to Warriors in coming years.
The 24-year-old has previously won the Player of the Year award at the club.