Quintilla, 23, renewed his contract in February and has appeared more for Villarreal than ever before this season.
And with Villarreal overbooked in the left-back position, Quintilla is being allowed to leave.
Quintilla represented Spain up to under-19 level and joined Villarreal from Barca in 2017.
Norwich have now confirmed the loan signing of Quintilla from Villarreal, saying they have an option to buy him.
Quintilla likened the Canaries to Barcelona and Villarreal in his first interview.
“My philosophy and my football is similar to Norwich’s,” he said. “I played before for Villarreal and Barcelona’s academy, and I think Norwich works a bit like them, so it’s great for me.
“I come here to play as many minutes as possible. We want to play good football for the fans to see.
“I would love to play in the Premier League, so I will do everything possible to get Norwich into the top league.”
🤝 Time for another summer signing…
We're delighted to welcome Xavi Quintilla to Norwich City on a season-long loan from Villarreal! 📝
🇪🇸 #HolaXavi 🇪🇸
— Norwich City FC (@NorwichCityFC) August 18, 2020