The defender is yet to make a league appearance for the Cherries, but played in every match of the club’s run to the Capital One Cup quarter-finals last season.
His performances in that cup run earned him a call-up to Aidy Boothroyd’s England U20s squad and Bournemouth boss Eddie Howe has moved quickly to secure Cargill on a new long-term deal that will keep him at the Vitality Stadium until the summer of 2018.
Cargill, a product of the club’s academy, netted on his debut for Boothroyd’s England side against Canada back in November and also featured for the Three Lions in this summer’s Toulon tournament.
The 20-year-old is delighted with his new deal and told the club’s official website: “I’m really pleased as it’s another good moment for me.
“I’m thankful to the club and the manager for showing faith in me and offering me a new deal. The gaffer always says that if I work hard, he will reward me on and off the pitch.
“I’m glad he has stuck by his word and it makes me want to work even harder. I’ve always wanted to play in the Premier League and to be offered a contract as a Premier League player is amazing.
“I hadn’t heard of any interest (from other clubs regarding a loan move) and it would have been nice if there had been, but I want to stay here.
“I want to get into that team and play week in week out. My aim has always been to play for Bournemouth and I want to prove I’m good enough.
“I do sit at home sometimes think that this time last season I couldn’t imagine being in this position.
“It’s been an amazing year, and the England call-ups were crazy, but I’m enjoying it and taking it all in my stride.”