Lemina succeeds Max Kilman after the defender's sale to West Ham.
Lemina told the club's website: "I feel proud. It means a lot for me because I’ve been working really hard for the group. I’ve been one of the leaders, one of the most contagious players in the team. I have a really good relationship with the Gaffer and the players, so I can be in between and try to transmit the best message for both.
“We talked about it last year because I was one of the leaders. Max was the captain and he’s been really important for us, but I was contagious for the players, the way I behave, the way I train, the way I do my stuff on and off the pitch.
"I try to transmit things to the others. Everyone was happy, but normal. They already knew from last year who I was and what I can give to the players on and off the pitch.”
The decision was made by manager Gary O'Neil and Lemina added: “Gary, for me, is a fantastic manager. To be honest, he’s the type of manager I want to be when I become a manager hopefully one day. He understands players, he knows how to talk with players, he recognises when we do mistakes, and we can talk. I think it’s about trust and that’s what we’ve found with Gary.”