The Newcastle United defender will rejoin his former loan club on July 1 when his contract at St James’s Park ends.
Cass saw his spell at Vale Park cut short by injury last season, and the 22-year-old was keen to return to the club, which won promotion to League One through the play-offs.
“On the back of how successful everyone was last year, I’m delighted to get it (the move) over the line and enjoy my next couple of years here,” Cass told the club’s YouTube channel.
“I did go to a few games of the opposition we were going to play I sent my reports back to Crosser (assistant manager Andy Crosby).
“I enjoyed it less watching the last little bit of the season. I was messaging Deano (first-team coach Dean Whitehead), and saying ‘I hate watching this on TV – I’d rather be a part of it’.
“It did kill me a bit but I was buzzing that everyone went up and I was delighted watching all the celebrations.”
Cass was offered a new deal by United, but the North Shields-born player felt a move to Vale was the best for his career.
“The club’s definitely going in the right direction,” said Cass. “There is no stopping it, the way the tight-knit group is around the building - the staff, everyone from top to bottom. It is a family club and I have absolutely loved my time here.
“I wanted to come back, this was the first option. Hopefully we can go in the right direction again and push on. I am excited to see everyone.”
Cass – who had a loan spell at Hartlepool United the season before last – posted a message to Newcastle on Twitter after the move was confirmed.
“Would like to thank everyone associated with @nufc during my last 10 years at this great club,” tweeted Cass. “From the players in the changing room to the staff around the building thank you for making my time there special. Time for a new challenge @OfficialPVFC.”
Cass joined United at the age of 12 after starting out at North Shields Juniors.