The 28-year-old flanker is delighted with his promotion, with the Scarlets poised for another season of high hopes of success following their Celtic League championship triumph last term.
But now the Scarlets have targeted a successful run in the Heineken Cup as their primary target in the tournament's 10th season.
Easterby may be new to captaincy, but knows the strong Scarlet squad around him will pull together as the West Wales region embarks on what will be a long and difficult season.
"We've got our work cut out this season with a tough European group and defending the Celtic League title, but we're a determined bunch," he said.
"There's a lot of experience in the side which I'm hoping will make my life easier."
Easterby has received backing from Scarlets coach Gareth Jenkins: "Simon is the consummate professional and has the total respect of the whole squad as well as the coaching staff."
He succeeds centre Leigh Davies, who is taking a year off from rugby.