The six-foot-four champion and six-foot-five challenger both weighed in at 204.5 pounds, under the 205-pound limit.
The weigh-in for Saturday's fight was conducted in front of a good crowd outside at Maple Leaf Square, adjacent to the Air Canada Centre. UFC president Dana White wore a Maple Leafs jersey for the occasion with No. 13 and White on the back.
A smiling Jones blew a kiss at the fans as he bounded onto the stage. Then he tossed his running shoes and "Not Quite Human" Nike T-shirt into the crowd.
Gustafsson (15-1) came out holding a scarf in Swedish blue-and-yellow colours.
Jones (18-1) did not make eye contact with the big Swede as the two posed, his eyes instead seemingly burning a hole in Gustafsson's chin.
When the two separated, they did not shake hands. Jones bent down, clapped his hands and let out a whoop.
The champion drew some boos as well as cheers. Gustafsson got some loud cheers from Swedish fans in attendance.
Much has been made of the fact that Jones does not have his usual size advantage against Gustafsson.
But both fighters dismissed the height factor.
"This sport's about intelligence and the way you approach this game," Jones said after weighing in. "I am so ready. I'm so excited to prove that height really doesn't mean that much."
Said Gustafsson: "It's all going to go down to who's been working the hardest and wants that belt more."
Interim bantamweight champion Renan Barao weighed 135 pounds while co-main event opponent Eddie Wineland was 135.25. The two got up-close and personal but still shook hands after they squared off.
Montreal bantamweight Ivan (The Pride of El Salvador) Menjivar weighed in at 137, meaning he had to lose another pound within an hour to make the limit.
That didn't stop him from donning a futuristic mask over his mouth as he posed with Wilson Reis.
Russian lightweight Khabib (The Eagle) Nurmagomedov also used a prop, walking on stage in a white fur hat. He took it off when he stepped on the scales but good-naturedly gave it to opponent Pat (Bam Bam) Healy to wear when they posed at the side of the stage.
Matt Mitrione and Brendan Schaub, former friends on "The Ultimate Fighter" show, continued the ill-will shown in the leadup to their fight. The two heavyweights did not shake hands and exchanged words after posing.
Schaub has disrespected Mitrione's work ethic, among other things. Mitrione has questioned Schaub's chin.
Mitrione, who did not bother to shed his jeans before stepping on the scales, weighed 260.5 pounds to Schaub's 237.
The card is the UFC's fourth in Toronto and 14th in Canada.
UFC 165 weigh-in results
Jon Jones (204.5 pounds) vs. Alexander Gustafsson (204.5)
Renan Barao (135) vs. Eddie Wineland (135.25)
Matt Mitrione (260.5) vs. Brendan Schaub (237)
Francis Carmont (186) vs. Constantinos Philippou (186)
Pat Healy (155.75) vs. Khabib Nurmagomedov (156)
Myles Jury (156) vs. Mike Ricci, Montreal (155.5)
Ivan Menjivar, Montreal (137) vs. Wilson Reis (135)
Chris Clements, London, Ont. (169.5) vs. Stephen Thompson (170.5)
Mitch Gagnon, Sudbury, Ont. (136) vs. Dustin Kimura (136)
Renee Forte (155.5) vs. John Makdessi, Montreal (155)
Michel Prazeres (155) vs. Jesse Ronson, London, Ont. (155.5)
Alex Caceres (136) vs. Roland Delorme, Winnipeg (136)
Nandor Guelmino (230) vs. Daniel Omielanczuk (245.5)