The transfer fee can increase to 19 million euros ($21.60 million) including bonuses. This would mean a record fee in Feyenoord's history, reports Xinhua news agency.
Karsdorp already underwent a medical on Tuesday and signed a contract for five years until mid-2022 on Wednesday. In Rome, he will meet his compatriot Kevin Strootman, who left PSV for AS Roma in 2013.
"Coming to AS Roma is a great step forward for me," Karsdorp said on the website of Roma.
"I come here with a great desire and enthusiasm to play and to realise my dreams. I know I still have a lot of room to improve and I hope to do that here."
Three-times Dutch international Karsdorp made his first team debut for Feyenoord in August 2014. In total, he has played 78 league matches for the Rotterdam based club, in which he scored once.
Last year he won the Dutch Cup with Feyenoord and this year he captured the Dutch championship.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
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