Leclerc finished ahead of teammate Carlos Sainz (29) but with the Spaniard having a ten-place grid penalty imposed after Thursday's practice, world champion Max Verstappen (26) of Red Bull will start second.
Mercedes' George Russell (25) will be in third place on the grid alongside Alpine's French driver Pierre Gasly (27).
There was little to choose between the two Ferrari drivers with Leclerc, who topped all three segments, posting a fastest lap of 1:32.726 and Sainz just 0.044 off the pace.
Three-time world champion Verstappen pulled out of his final lap but will back himself to once again overcome Leclerc on race day.
"It was enjoyable out there. I think we maximised today. I think the whole weekend so far we have been lacking a bit of one-lap performance and that was quite clear," said the Dutchman.
"I hope tomorrow in the race we are good on the tyres again and can work our way forward," he added.
Leclerc had mixed feelings after his run in the final qualifying segment.
"To be starting from pole is great. However, I'm a bit disappointed about my laps in Q3. I didn't do a good enough job but it was enough for P1 and that's all we need," he said.
"Now it's full focus to try and put everything together for the race. Normally, that's where we lack most performance so I hope we can put it all together and win here," he said.
After the embarrassing start to the new Vegas event, when Thursday's opening practice was abandoned after nine minutes due to loose drain covers on the track, fans finally got to see some action on the new street track.
The second practice session had been held in front of empty stands and did not finish until 4am in the morning local time but the crowd were more than happy to see F1's stars battle for grid position at midnight.
Powering down the famous 'strip' past landmark hotels and cornering around the striking new illuminated 'sphere', there were no signs of major problems with the surface.
Both McLaren drivers, Lando Norris (23) and Oscar Piastri (22), were eliminated after Q1 and they were followed by Red Bull's Sergio Perez (33) and seven-time world champion Lewis Hamilton (38) of Mercedes after Q2.
Sainz received his 10-place grid drop after his team were forced to make repairs to his car after the chaotic first practice.
Sainz's car hit a loose drain cover and suffered damage and the team had to change a host of power unit components in order for the Spaniard to continue.
But with Sainz using his third energy store of the season, one more than is allowed by regulations, he was handed the penalty.
