Briton Norris, fresh from his dominant Mexico City triumph which put him one point clear of Piastri with four rounds remaining, carried on where he left off at Interlagos, recording the two fastest laps in Friday's final qualifying session.
Even though Piastri looked in much sharper form than in his recent underpaced efforts in Austin and Mexico City, he still couldn't match his flying teammate when it mattered most, as his best effort also still put him behind Mercedes' Kimi Antonelli.
Norris's best of 1min 09.243 sec put him 0.097sec clear of Antonelli, while Piastri was 0.185 seconds off his teammate's pace.
So Norris will have the advantage as the two contenders battle for crucial points in the 100km sprint on Saturday when eight points will be on offer to the winner and when all the first eight across the line will score.
Despite coming off second-best again, Piastri didn't sound too worried about a day when he had almost matched Norris in the earlier practice session, with the Briton leading the timesheets on 1:09.975 to the Australian's 1:09.998.
"The soft (tyre) just was a bit different from what I expected," he shrugged about his final run.
"A couple of big moments on my first lap which wasn't ideal, and that was a bit of a shame, but ultimately, I felt much happier today than the last couple of weeks.
"Practice went very well, we changed a few things for qually, which took a little bit of getting used to again, but ultimately I'm pretty happy.
"Would have liked a little bit more, but we can definitely fight with what we've got and there's obviously a lot more points on Sunday (for the main race)."
There's a chance of the weather turning too, with wind and rain forecast for Saturday. "It's going to be an interesting day. Let's see what weather we get. But I'll try and take whatever opportunities there are," added Piastri.
"I think the pace in the car has been really good today, so hopefully that translates."
"It was a little bit tougher than I would have liked, close between lots of cars - Mercedes were quick on the softs," a delighted Norris said. "But we did the job we needed to do."
Defending champion Max Verstappen is also still in contention in third, 36 points behind Norris.
But the Dutch Red Bull ace will start the sprint in sixth after moaning to his engineer at one point: "The car is completely broken. Just undriveable."
George Russell in the other Mercedes and Aston Martin's Fernando Alonso were fourth and fifth, with Aston Martin's Lance Stroll, Ferrari's Charles Leclerc, Racing Bulls' Isack Hadjar and Nico Hulkenberg in the Sauber rounding out the top 10.
A spin from Leclerc left Ferrari team-mate Lewis Hamilton no time to get in a final flying lap and he found himself eliminated in the second part of qualifying.
