Arsene Wenger's side have failed to win a trophy since beating Manchester United in the 2005 FA Cup final, despite at one stage being on course to win four trophies this season before the wheels fell off.
The French boss is under pressure to invest in a squad that badly fell away during the back end of the season, and Walcott says the club have to look to strengthen.
"Yeah, I'm expecting players to be signed,, the manager's said so," Walcott said.
"Hopefully we can keep hold of our best players, as we need to be winning something next season without a doubt. It's been so long and the fans have waited so long. And players don't like seeing every season go without winning anything."
While Wenger may be intent on bringing players to the club this summer, his biggest fear may lie with the future of Samir Nasri, who has been heavily linked with a move away from the Emirates Stadium, and Walcott hopes the midfielder can stay at the club.
"He had a great season, he showed people what he can do. He's a very important player to Arsenal and we'll see what happens in the summer."