The 31-year-old has made 326 appearances for the club since joining from Sunderland in 2017.
His contract had been due to expire at the end of the 2026/27 season.
"I'm delighted," Pickford told evertontv. "Delighted to get it done - it's an extra two years, so four years in total.
"I'm over the moon and it gives me the opportunity to build a legacy for myself here, move forward and build this club to where we want to be.
"Everton is a really special club to me. Coming from Sunderland as a young lad and growing into a man here, it's been a special time for me and my family."