North Walian-born McCusker, 26, has appeared 68 times in the Scarlets shirt with 15 points and has won four caps for Wales - his debut for his country coming in 2010 against South Africa.
Scarlets Head Coach Simon Easterby, himself a former international and Scarlets flanker and captain of the Scarlets for five consecutive seasons said that Rob McCusker was a 'natural leader' that had earned the respect and support of his colleagues through hard work and commitment.
Simon Easterby said: "Having played alongside Rob and then also coached him as a player, I have seen him develop and mature as a player a great deal over the past six years.
"He has certainly earned his stripes working extremely hard to get his opportunity with the Scarlets and once he did he hasn't looked back. He is a true Scarlet in terms of his values and commitment to this squad, our region as a whole and its supporters and he will have the full support of all the players in his captaincy.
"He has the respect of his peers and coaching group which is vital and he will lead the team from the front and by example and I know will set the highest of standards along the way."
Easterby added that McCusker's appointment as captain shows the progression of the squad and the need for a leader with the ability to bring forward and connect with a number of younger players as well as having the backing of senior Scarlets colleagues.
He added: "We have a young team with some natural leaders in it, and with Rob at the helm it's only going to get better.
"We thank Matthew Rees who has done a great job over the past two seasons as Captain at a very key time in our progression - bringing a level of mental toughness and setting high standards in leading our squad.
"Matthew was intent on seeing the team build strong home form at Parc y Scarlets last season and he continues to add weight and experience within the team as to what we want to achieve in terms of performance. He is totally supportive of Rob being handed this opportunity as captain and is backing him 100% along with all the Scarlets players."
McCusker, from Wrexham began his playing career with Mold RFC and after being spotted by the Scarlets he made his debut for the region in August 2007 against Exeter Chiefs.
A Wales age-grade player, McCusker has achieved international honours with the Wales under-20's then Wales 7's team and more recently under Warren Gatland earning four caps for Wales including his most recent against the All Blacks in Hamilton in June 2010.
A committed and respected Scarlet, McCusker said he was "delighted" and "honoured" to have been handed the captain's armband next season and that he was excited by the challenge.
He said: "It's a big honour and privilege to be asked and I was delighted to be picked as Captain after six season in the Scarlets shirt; this region has supported me well as a player coming through and backed my progression and I will give it everything I can to help lead our team and work hard alongside the boys to see us achieve our potential and push forward in 2012/13.
"We've got plenty of spirit in this squad and it's an exciting time ahead - the players are really looking forward to what we can bring to this new season's campaign and working with Simon, Mark and Danny Wilson who bring a real energy, ambition and focus as coaches."
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