Yachvili kicked over 13 points against his former club at Kingsholm Stadium as the French side earned a 41-31 victory.
"We are very happy," he told Sky Sports News. "We knew that Gloucester were playing well in the Premiership, so this is a very good win for us.
"We are the cup holders, and we know if we win the tournament we will qualify for the Heineken Cup next season. We will keep working hard."
Yachvili spent one season at Gloucester before his move to Biarritz in 2002.