The Australian will line up alongside Ferrari's pole-sitter Charles Leclerc at the Hungaroring on Sunday with title rival and teammate Lando Norris in third place.
"Pretty confident," Piastri, 16 points clear of Norris, said of his chances of taking a seventh win from 14 races.
"It was good last year, so hopefully it can be good again this year."
Piastri started second last year, with Norris on pole, and went on to take the first win of his F1 career.
Sunday's race could see some rain, which could make things tricky on a twisty circuit where overtaking is already difficult and strategy can be crucial.
McLaren were fastest in all three practice sessions but Leclerc made the most of the conditions to seize a surprise advantage.
"If you're sat where Charles is, fantastic. If you're sat where I'm sat, bizarre and somewhat frustrating," he said when asked to sum up the session. "I think the conditions completely changed, and it was just weird.
"I think our pace has been good, but Charles has been quick all weekend, in certain sessions," added the Australian. "It is a very difficult track to overtake on, and it's not going to be the easiest place to try and regain the lead."
Norris, winner of four races so far this campaign, agreed with his teammate.
"I think we always have, at least in the race, a bit more of an advantage. But our main competitor over the last four, five races has been Charles and it's been the Ferrari," said the Briton.
"So, if there was anyone else that's going to be on pole today, it was going to be Charles. And if there's anyone that's going to make our life tough tomorrow, it's going to be the same guy."