The "feisty fittie", who joined the show in series two, announced the news on Twitter earlier today.
"I'm leaving Geordie Shore! I've had a mint time - Cancun was crazy and I'm glad to be going out on a high. Big thanks to all my fans," said Walker.
"You haven't seen the last of me, looking forward to future projects."
Her co-star James Tindale tweeted back: "You will be a miss Becca, all the best for the future."
Charlotte-Letitia Crosby added: "[Rebecca is] an amazing gorgeous and strong little fire cracker. Never a dull moment, love her rants, she has me in stitches. Not going to be the same being in a room and you not being there. It's always been me, you and Holly in our tip of a room eating Big Macs in bed."
Walker's departure follows the announcement that original cast member Jay Gardner will also be leaving the show.
MTV confirmed earlier this year that it was recruiting new stars for the fourth run of the show, which will be filmed during the summer.
Geordie Shore: Chaos In Cancun is currently airing on Tuesdays at 10pm on MTV.
