"I still have the drive, passion and energy to want to get better and strive to perform for the team," Trescothick told Somerset's website.
"I'm delighted to have signed for at least another year. I'm excited for what is to come for the club when you look at the combination of youth and experience within the squad," he added.
"When you think of Somerset County Cricket Club you think of Marcus Trescothick. His work ethic is second to none and you simply can't measure what he brings to the Club behind the scenes and in the dressing room. He is the epitome of what a professional sportsman should be," said Andy Hurry, Somerset’s Director of Cricket.
"We had a number of discussions throughout the season and he made it very clear that he still has the drive and he wants to continue playing whilst he can still positively impact games," he added.
Trescothick made his first-class debut in 1993, two years after joining Somerset and has gone on to score more than 26,000 runs in the longer formats of the game.
The 42-year-old made 76 Test appearances for England, scoring 5,825 runs in an international career that ran from 2000 to 2006.
He was also a member of the England cricket team that won the Ashes against Australia in 2005 in what was a memorable series.
This season has seen him make nine appearances in the County Championship in which he scored three half-centuries and one century for Somerset.
First Published: September 26, 2018, 9:30 AM IST