The Panthers looked dead and buried when they trailed 24-8 at the hour mark with Cleary's halves partner Jarome Luai off the pitch injured at Stadium Australia.Cleary took the game by the scruff of the neck, however, to almost single-handedly bring a fifth title to the club from Sydney's western reaches.
His break set up a try for prop Moses Leota in the 62nd minute, his playmaking crafted an opportunity for centre Stephen Crichton to score a second and the halfback himself scurried across the line for the third.
Cleary converted all three with his unerring boot, the last one sealing the first hat-trick of successive NRL titles since the Parramatta Eels of the early 1980s.
"It feels like a dream at the moment," said Cleary after sharing a hug with his father, Panthers coach Ivan.
"We're down but we're never out, that's our mentality. We just had to keep fighting, that's what we do."
After an unseasonably hot spring day in the harbour city, the match kicked off in temperatures of 30 degrees Celsius with the intensity of the early exchanges matching the atmospheric conditions.
Penrith hooker Mitch Kenny opened the scoring with a try in the 17th minute after Brisbane botched a line dropout and Cleary added a penalty on the half-hour mark.
Brisbane prop Thomas Flegler crashed over the line under the posts just before the break to cut the deficit to 8-6, however, before Broncos five eighth Ezra Mam put his stamp on the game early in the second half.
The 20-year-old Torres Strait islander, an unheralded member of a team studded with outstanding young backs, showcased his explosive speed to score three tries in 10 minutes.
Mam looked like being a shoe-in for the Clive Churchill Medal as Man of the Match until Cleary snatched it from him in 18 remarkable minutes.
"Jeez we let that one slip," said Broncos halfback Adam Reynolds. "Can't fault the effort but that's a hard one to take."
