The midfielder has been named in Roy Hodgson's squad for the tournament in Brazil following some impressive displays for the Toffees this season.
However, Naismith believes that the hype could prove to be a distraction for the 20-year-old.
He told Sky Sports News: "Playing for Everton much more this season has definitely made a big difference for him. He's a player with an unbelievable amount of talent and rightly deserves to be at the World Cup.
"There's a lot of pressure that gets put on him. Without doubt, he's got the talent but I don't think there should be as much pressure put on him.
"Just let him go and play. I'm sure the manager will play him when he sees fit and when it's right but he's a massive player now and he's only going to get better."
Barkley scored seven goals in 38 appearances for Everton during the 2013-14 campaign.