North Walian McCusker, who joined the region's academy a decade ago, is currently in his second season as club captain whilst Neath born winger Phillips is looking forward to a third season with the West Wales region.
The news sees both players added to a list of contracts already secured with key players including Wales internationals Rhys Priestland and Scott Williams, in-form scrum half Gareth Davies and All Blacks international Regan King already in place for the new season with more announcements still to come.
Scarlets Head Coach Simon Easterby said: "We are delighted to have retained both Rob and Kris on extended contracts here at Parc y Scarlets to maintain balance and experience in our squad.
"Rob has led the team with spirit this season and is a true Scarlet in terms of his values and commitment to our squad, the region as a whole and our supporters. He has worked hard to get his opportunities with the Scarlets over recent years and has taken to leadership and the responsibility of captaining the squad well.
"Kristian has settled in well since joining us a few years back and has made the most of the opportunities handed to him here at Parc y Scarlets. He's reignited his spirit for the game, shown a good work ethic, ambition and enthusiasm and has bought into our Scarlets values and goals as a team.
"He's still a young talent and offers real attacking options in the back-three alongside Liam, Jordan and Frazier."
Easterby added that there were still more names to unveil in coming weeks for the Scarlets but only when the Region was ready.
"We have repeatedly stated our commitment to recruitment from outside to strengthen key areas of our rugby group for next season. That continues as part of our strategy to retain key experience at Parc y Scarlets as well as build and strengthen our squad for next season with some new players."
McCusker, 28, from Wrexham began his playing career with Mold RFC and made his debut for the region in August 2007 against Exeter Chiefs. He achieved international honours with the Wales U20s then Wales 7s team. He has six senior caps for Wales.
Speaking about the news McCusker said: "I'm happy to be staying at the Scarlets - my heart is in the Scarlets Region and at home in Llanelli and I feel I still have unfinished business here particularly after being handed the privilege of being captain.
"We've got plenty of spirit in this squad and we want to get the Scarlets back to where we should be in world rugby. There's no doubt we are building a great team and I wanted to continue to be a part of that.
"Next season will bring new challenges and excitement and with a core of players still retained together as well as some strong additions to the group we'll go into next season with real energy, ambition and focus."
Pacey winger Kristian Phillips, who achieved international honours with Wales U20s, joined the Scarlets for the 2012-13 season and has gone on to make 37 regional appearances scoring four tries. A spectacular individual try saw Phillips help is side to victory against Racing Metro away from home in the Heineken Cup pool stages earlier this season.
Phillips said: "The opportunities I've had so far here with the Scarlets has really brought me on again and I'm delighted to have the chance to extend my stay at the region.
"When the opportunity came to join the Scarlets a couple of years back it was one I couldn't turn down. With the history and philosophy of running rugby I couldn't wait to get down here and I've really enjoyed my time here so far.
"It was somewhat of a frustrating start to the season due to injuries but things have been going well since then. It's been down to me to do my best on the pitch and I'm working day in day out on technical aspects of my game to improve.
"I'd like to think that I can contribute to a couple of victories at the end of the season to ensure that we finish on a positive note."
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