The 25-year-old made his debut for Durham in 2015 and has become a regular first-team player across all formats during the last two seasons.
Clark’s impressive performances as an opener in this season’s Vitality Blast, where he scored 408 runs, including three half-centuries, helped Durham secure a home quarter-final and saw him develop a strong top-order relationship with New Zealand international Tom Latham.
Clark has scored over 1200 first-class runs over the past two Specsavers County Championship seasons and he averaged 39.28 in the 2017 Royal London One-Day Cup.
“I’m delighted to be extending my contract with Durham and excited to help the team compete for silverware next season,” Clark said.
“Emirates Riverside is a special place to play cricket and I can’t wait to get back into training with the lads and continue to develop my skills.”
Durham County Cricket Club, Head Coach, Jon Lewis, said: “We’re happy that Graham has extended his deal and I am confident he will continue to demonstrate his ability over the next few seasons.
“Graham has proven over a number of years his ability in T20 cricket and we began to see his talent flourish last year.
“The challenge for him going forward is to establish that kind of form across three formats.”
© Cricket World 2018