Amat has followed the example of his countryman Angel Rangel by committing to a one-year extension which will keep him at the Liberty Stadium until 2018.
"I'm so happy because it's important to know the club has confidence and faith in me," Amat told the official club website.
"It was a big decision to move my family here
I was moving to a new country and a new league, but it has worked out really well.
"I've played games in the Premier League, the cups and the Europa League, so it has been an amazing experience for me here already.
"But this is hopefully just the start."
Amat joined Swansea from Primera Division club Espanyol for £2.5million in the summer of 2013 and made 30 appearances in his first season in south Wales, mostly in his preferred position as a central defender but also as a holding midfielder.
The 22-year-old started the current campaign alongside skipper Ashley Williams at the heart of the Swansea defence but has struggled to win his place back since suffering knee ligament damage in September
"The injury was a tough moment for me, but it happens in football," Amat said.
"You just have to keep working hard and along with the support of the club it makes you stronger.
"Things can change quickly in football, and you need to be ready and prepared to play in every single game."
Source : PA
Source: PA