Bristol Rovers captain Tom Lockyer has signed a new undisclosed-length deal with the League One side, while Bernard Mensah has joined from Aldershot.
Ex-Watford striker Mensah, 23, has joined for an undisclosed fee.
Centre-back Lockyer, also 23, has made 200 league appearances for Rovers since his debut in 2013 and won his first senior Wales cap in November 2017.
"Tom is an established first-team player who's only getting better," boss Darrell Clarke told BBC Radio Bristol.
"He's very highly rated, he's a Welsh international, he's played 200-odd games and he's still young so we're delighted that the captain, the lynchpin of the changing room, has committed to the club long term."