The new deal will see the Shoreham-born bowler stay at The BrightonandHoveJobs.com County Ground until at least the end of next season.
The 23-year-old, who lives in Upper Beeding, signed a three-year contract with the club in 2010 - the year he made his first-class and LV County Championship debuts for the county.
Hatchett said: “I’m delighted to have signed a new contract with my home county. I felt I made plenty of progress last season, particularly with breaking into the one-day teams and playing more white-ball cricket.
“I look forward to pushing for a place in all three formats of the game and helping Sussex to be successful.”
In 2013, the seamer broke into the one-day set up for the first time, making his bow in both List A and Twenty20 cricket.
He also impressed in the Tour Match against the Australians at Hove as he claimed top-order scalps in both innings.
Sussex’s professional cricket manager Mark Robinson said: “Lewis showed real signs of progress last year and we hope with another good winter behind him he will really start to impact in all forms of the game next season.”