Though he was relegated to fifth, Piastri qualified on the front row of the grid, just 0.074s slower than Max Verstappen, at the Emilia Romagna Grand Prix last weekend.
In the race, his McLaren team-mate Lando Norris came within a second of victory, just two weeks after his maiden F1 success in Miami.
McLaren has demonstrated itself to be a front-runner and, in recent races, and has arguably emerged as the nearest challenger to Red Bull Racing.
“We can definitely be confident going there,” Piastri said as the F1 circus heads to Monaco.
“Obviously Red Bull had a difficult start to the weekend [in Imola], but that’s two weekends in a row where they’ve looked not quite as strong as they once were.
“We’re definitely closing in. I think us and Ferrari are putting them under pressure and I think as a team, McLaren, we can be very confident wherever we go.
“Monaco will be hopefully a good weekend.”
Last year’s Monaco Grand Prix was a breakthrough event for Piastri.
The rookie made strong gains throughout the early part of the weekend, missing out on Qualifying 3 to team-mate Norris by 0.018s.
It was a lap that followed a traditionally steady build up through practice before the young Australian pulled out an impressive time – going well over a second faster than he’d been on any lap earlier in the weekend.
Heading back to Monaco, Piastri will don an Ayrton Senna-inspired helmet design, incorporating the Brazilian’s famous yellow with blue and green stripes. He’ll drive a similarly themed car for the weekend too.
“Obviously everyone will know exactly what these colours represent,” he said in a video posted on social media.
“Since it’s been 30 years since the passing of the great Ayrton Senna, I thought it would be a great time to do a tribute helmet to him, and obviously the car that we are running this weekend, the livery and tribute to Ayrton, I thought it would be rude to not join in with the helmet.
“It’s my standard livery, more or less, with Ayrton’s colours and the colours of Brazil, still keeping the main design of my helmet.”
Opening practice in Monaco begins on Friday at 13:30 local time (21:30 AEST).
Eu amo esse capacete (hope that’s right) 🇧🇷 pic.twitter.com/n0BjbMBAEQ
— Oscar Piastri (@OscarPiastri) May 22, 2024