The 21-year-old, who is heading for Australia with the National Academy squad, is now committed to the club until the end of the 2008 season.
"I feel good about playing for Essex because we are winning trophies and getting through to the latter stages of competitions," he told the club's website.
Bopara was a member of the side which won the Natwest Pro40 title last summer.
He also produced career-best performanes in the Championship by scoring 159 against Glamorgan at Cardiff and taking 5-75 against Surrey at Colchester.
Extensions for Kent trio: England wicket-keeper Geraint Jones, England batsman and Kent skipper Robert Key and South African batsman Martin van Jaarsveld have all signed contract extensions with Kent.
The new deals will keep the trio at the club until the end of the 2009 season.
"Robert, Geraint and Martin have each made outstanding contributions over recent years.
"I am delighted we have such a strong nucleus of players who buy into the future vision of the club," said chairman of cricket Graham Johnson.
He confirmed Kent had made contingency plans in case it appears Jones, who will start the forthcoming Ashes series in Australia as England's first-choice keeper, will be unavailable for a large part of the 2007 season.
The 30-year-old is currently the only keeper on the staff following the decision to release Irishman Niall O'Brien.