Young's switch to Old Trafford was confirmed last week, but fears are growing that United's Portuguese star could leave the club as competition for places hots up, but Nani has moved to quash rumours of any unrest.
"Of course I have to welcome everyone they sign, I think Man United is a fantastic club," said Nani.
"When they bring in new players, they know if it is good for the team or not, and this (Young signing) has to help them. It is good for the team, we want more players to help us to win trophies."
The 24-year-old is no stranger to stern competition in the United first-team after having played second fiddle to Cristiano Ronaldo, who won the Ballon d'Or in 2008, before his move to Real Madrid.
"I've been there (at United) when Cristiano was there, Cristiano was one of the best players in the world," he added. "At that moment I had no worries about him taking my place."