He has scored nine tries so far this season - third in Super League’s list - and will now stay at KCOM Stadium until at least the end of 2023.
Swift, 28, joined Hull from St Helens ahead of last season but had a frustrating campaign for myriad reasons.
However, he has become a regular under new head coach Brett Hodgson and said: “I’m loving my time here at the club.
“I’m playing some of my best rugby in 2021, so the decision to extend my contract was an absolute no-brainer for me.
“Yes, 2020 was a tough first season for me with my various injuries, but this year has been like a fresh start and I’ve found a new lease of life out on the field.
“I feel my performances have reflected that.
“We’ve a great bunch of lads and a new coach who is implementing some really great ideas. We’ve started laying the foundations for something special – it’s a team I undoubtedly want to continue to be a part of.
He added: “I’ve got my own little family here in Hull now, and they’re really happy and settled here, and that made the decision a lot easier for me.”
Hodgson said: “I’m really happy with Adam’s form this season.
“He has applied himself extremely well and is getting the rewards through his performances.
“He had the ability to play a number of positions which we saw against Wigan in the Challenge Cup, which benefits both himself and us as a team. I’m looking forward to seeing Swifty continue his form and get the success he deserves.”
Yesterday’s home game against Leigh Centurions was postponed after Hull saw a third player test positive for Covid.
It left them without 19 first team or senior academy players due to Covid protocols/injuries and Thursday’s derby at Hull KR is in doubt.