Norris clocked a best lap in one minute and 11.799 seconds to outpace Leclerc by 0.078 seconds with Mercedes' George Russell a tenth adrift in third place ahead of Lewis Hamilton, the seven-time champion showing revived pace in his Ferrari.
It was an intriguing and closely contested hour of action that suggested all of the leading four teams are in contention to take pole position in qualifying later on Saturday.
Four-time champion Max Verstappen was fifth for Red Bull ahead of two-time champion Fernando Alonso of Aston Martin, Kimi Antonelli in the second Mercedes and championship leader Oscar Piastri in the second McLaren.
Piastri was seven-tenths adrift of team-mate Norris, who trails him by 10 points at the top of the drivers' championship after nine of this year's 24 races and endured what he described as his "worst Friday of the season" the previous day.
Carlos Sainz was ninth ahead of his Williams team-mate Alex Albon, pushing impressive rookie Isack Hadjar of RB down to 11th in front of another big crowd at the Circuit Gilles Villeneuve.
Overnight news of the FIA's decision to suspend British steward Derek Warwick was a hot topic in the paddock, along with a two-year contract extension for the Las Vegas race, ahead of the session, which began hesitantly in mild and dry conditions.
The first drama arrived after 22 minutes when Piastri slapped the 'Wall of Champions'’ on exit from the final chicane, suffering a punctured rear tyre. He limped to the pits, dropping debris that triggered a six-minute red-flag stoppage.
After his complaints on Friday, Vertappen was still having issues with his brakes, grumbling about "lacking bite with this material" while Red Bull team-mate Yuki Tsunoda was in the pits and without a competitive lap.
Norris improved to go top with 12 minutes remaining.
