UFC president Dana White quickly separated the two at the UFC 158 official weigh-in on Friday. Diaz forcefully moved St-Pierre's arms away with his own when the two came together. Each came in on weight: Diaz at 169 pounds, St-Pierre at 170.
The fight is set to headline the UFC pay-per-view event, which takes place at Bell Centre on Saturday.
"I can talk as much as I want," St-Pierre said, when asked to give his final thoughts. "But tomorrow I'm going to walk the walk."
The fight between St-Pierre (23-2) and Diaz (26-8) has been years in the making. St-Pierre has successfully defended the UFC title seven consecutive times. Diaz held the Strikeforce welterweight title for nearly two years before vacating it in 2011.
The UFC has tried to pair the two before. A title bout fell apart at UFC 137 when Diaz did not show for a news conference. Another meeting at UFC 143 was scratched due to a knee injury suffered by St-Pierre.
Diaz, like St-Pierre, kept his final words on the fight brief.
"I'm going to get out there and fight," Diaz said. "We're going to see what happens."
In the co-main event, welterweights Carlos Condit (28-6) and Johny Hendricks (14-1) will look to get into the 170-pound title picture. A lean Condit weighed in at 169 pounds. Hendricks weighed the welterweight maximum of 171 pounds.