The former England Under-20 international has made 116 appearances for the Sixways club and has become one of the key members of the side.
Over the last six years Arr has won both the Young Player of the Year and Player of the Year awards at Worcester.
Arr said: "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."
Head coach Richard 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."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.