The race started on a wet track, after a 28-minute delay because of the poor conditions.
Piastri made a better launch than Antonelli, and was alongside the Mercedes on the approach to the first corner, the position already won.
Antonelli claimed Piastri had pushed him off, but in fact ran wide off track on his own as Piastri assumed the lead ahead of Norris, Verstappen, and the rejoining Mercedes.
Piastri pulled out a four-second lead in the the first few laps but as the track dried Norris began to come back at him and the McLarens were running nose to tail when Piastri pitted for slick tyres on lap 13.
He was gaining on Norris and set to resume the lead until the accident between Alonso and Lawson, which will be investigated by stewards after the race.
Norris resumed with a two-second lead and as the race finished under the safety car the win was secured.
It was almost carbon-copy of his maiden win in the grand prix here last year, when a safety car vaulted him into the lead ahead of Verstappen.
“My luck in Miami seems pretty good at the minute,” Norris said, “but the pace was already pretty good. You never know when to pit, go early or late and wait for safety car. It has worked two years in a row. I would probably prefer it happened tomorrow (in the grand prix) rather than today but I’m happy.”
