WBA 'regular' champion Fielding was the first to step on the scales at Madison Square Garden, the Briton - who stopped Tyron Zeuge in July to claim the belt - registering 167.6 pounds.
"The weigh-in is done. The talking is done, [I'm] ready to fight now," the 31-year-old told DAZN.
Asked if he had studied footage of his opponent to prepare for what he agreed is the biggest fight of his career, Fielding replied: "I've watched bits, but I leave it down to the team. We work together and will have a plan for tomorrow."
Alvarez, meanwhile, weighed 167.4 pounds, unsurprisingly the heaviest he has been in his career as he prepares to fight up at super-middleweight for the first time.
The Mexican is attempting to become a three-weight world champion this weekend, hoping to add the 168-pound title after already securing belts at both light-middle and middleweight.
While neither fighter in the main event had any issues, Tevin Farmer had to strip naked to make weight for his clash with Francisco Fonseca on the undercard.
The IBF super-featherweight champion registered right on the 130-pound limit ahead of his title defence.