Sargeant made his debut in the Formula 1 support category in 2019, racing for Carlin Buzz Racing and scoring a best result of eighth in France and Hungary.
Sargeant tested with Prema at the post-season test in Abu Dhabi earlier this month, and becomes just the second confirmation on the 2020 grid.
Prema dominated the 2019 campaign, which was the maiden year for the newly formed F3 category, which merged the GP3 and European F3 championships.
The Italian squad won 50% of the races last season and ended the championship 304 points in front of Hitech Grand Prix, who finished second behind Prema.
“I am thrilled to be racing with Prema in 2020," Sargeant said. "Coming off the back of their dominant season in this exciting championship, I’m delighted to be given the chance to continue that success into next season.
“We have already had a great test in Valencia which went really well and we got some great times out of the car and worked very well together. My goal for 2020 is to keep working on improving myself on and off the track and ultimately helping Prema to retain the title.”
Team Principal Rene Rosin added: “We are very happy to welcome Logan to our team. He made a name for himself in karting competition and showed winning potential in all the championships he entered so far.
“For the first time in his career, he will not be a rookie in 2020, and we think his insight will be highly beneficial for him and for the whole operation.
"I am excited to see how our team is shaping up for 2020 and I can’t wait for the Team to get back on track after a very successful first season in the FIA Formula 3 Championship.”
Bahrain International Circuit - Winter testing
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