Born in Gloucester and a former pupil of St Peter's High School in the city, he returned to Gloucester in the summer of 2008.
Since his debut in the 1998-9 season, he has been a regular in the first team squad making over 200 appearances in total in all competitions scoring 10 tries in the process.
Eustace admitted that he was glad to put pen to paper.
"I've signed a new contract and I'm absolutely delighted to have done so. I've spent most of my career here so it was an easy decision."
"I can focus on the rest of the season now as we have some big games coming up and I'm determined to play my part."
Meanwhile, Eustace has been named captain of the Gloucester United side who take on London Wasps in Thursday night's Guinness A League semi final against London Wasps at Dry Leas, the home of Henley Hawks.