De Vrij has been closely followed in England with Manchester United, Liverpool and Everton all believed to be contemplating summer bids for the Dutch international.
Midfielder Clasie was wanted in Serie A with Fiorentina looking to take him, but now both players have extended their current contracts.
De Vrij has added a year to his terms taking him to 2015, while Clasie is now tied down until 2016.
"It makes me happy to know I can continue to be part of this team and club for longer," de Vrij stated.
"I can see the potential here and of course I am pleased that Jordy remains for longer here too."
Claise said: "It means a lot for me, I've played for Feyenoord for 14 years and it has been fantastic. I want to stay longer with this club, I'm really enjoying myself here."
Feyenoord chief Martin van Geel was delighted to tie down both players for an extended period.
"These are two of our main men in our team and we are very pleased with this looking ahead to next season," he added.
Clasie's agent Wessel Weezenberg confirmed that he thought long and hard about the possible move to Fiorentina.
"It was a sports and personal decision. He thought it was good for his career staying at least another season at Feyenoord, a great club with great fans, where he feels a key player," he told Calciomercato.
"His choice doesn't mean he wasn't interested in Fiorentina's proposal, they are a great team and Florence is a wonderful city. The Fiorentina's project fascinates him from every point of view, but he's still young: we will see what will happen next season."