Lynch’s original deal expired on the January 3, having joined the club in September. Since his arrival at The People’s Pension Stadium, Lynch has made nine appearances, scoring two goals from centre-back.
Lynch was most recently involved in the 3-1 victory against Colchester United, where he scored Crawley’s second goal of the afternoon.
The defender said: “It has been a long time coming to be fair, my first contract was short so I am delighted to get a new one sorted. It is exactly what I wanted, it is home for me and I have really enjoyed my time here so far.”
Manager John Yems said: “Joel spent a lot of time with us and earned his contract, he’s worked hard and has had a top career. He’s been a great influence around the place and will be a brilliant addition for a further 18 months, he’s a lad that brings a lot of professionalism to the club.”
Chief executive Erdem Konyar said: “I’m delighted that Lynchy has signed to stay on for another 18 months at the club. He is an important influence on and off the pitch.”
The club will be speaking to Joel at tomorrow afternoon’s press conference ahead of the Reds' League Two fixture with Northampton Town.
Meanwhile, Amrit Bansal-McNulty has returned to parent club QPR after his loan spell at Crawley.
The midfielder made seven appearances for the Reds in all competitions