All weigh-ins for Saturday's card at the Prudential Center went off without a hitch as every scheduled fighter made weight.
Jones, 23, walked toward the scales with a stern look on his face. His breathing was slightly rapid, which is the case before each of his fights.
Rua was the polar opposite of Jones. A veteran of many high-profile battles, Rua showed no outward signs of nervousness.
Both fighters weighed in at 205 pounds.
For the first time since Feb. 5 when Jones was offered the title shot, the 29-year-old Rua expressed disappointment at being an underdog to his younger rival.
"I really feel it is disrespectful," said Rua, who will bring a professional record of 19-4-0 in the Octagon. "This belt is mine and it will keep being mine after [Saturday] night."
The usually good-natured Jones (12-1-0) was all business at the weigh-in, knowing that his chance to become the youngest champion in UFC history was only hours away.
"I feel great," Jones said. "This is the biggest opportunity of my life."
Former WEC featherweight champion Urijah Faber, who now competes in the bantamweight division, tipped the scale at 135½ pounds.
Faber's opponent, Eddie Wineland, also weighed in at 135½ pounds. Wineland is also a former WEC 135-pound champion.
In the other fights on the UFC 128 main card, heavyweight Brendan Schaub (245 pounds) looked in tip-top shape for his battle against Mirko "Cro Cop" Filipovic (229 pounds).
In the remaining bouts, featherweight Erik Koch (145 pounds) faces Raphael Assuncao and Constantinos Philippou (195) meets Nick Catone (194) in a catch-weight fight.
Ian Loveland (135) and Joseph Benavidez (136) will face each other in a bantamweight battle. Lightweight Kurt Pellegrino (156) returns to action after a year-long layoff against veteran Gleison Tibau (155).
Rounding out the card is a welterweight bout between Mike Pyle (171) and Ricardo Almeida (170), a lightweight fight pitting Anthony Njokuani (155) and Edson Barboza (155½) and
Eliot Marshall (205) facing Luiz Cane (205½).
Franklin McNeil covers mixed martial arts and boxing for ESPN.com. He appears regularly on 'MMA Live,' which airs on ESPN2. Follow him on Twitter at www.twitter.com/Franklin_McNeil.