The 25-year-old was cleared to play only on Thursday after passing all concussion tests and took back the kicking duties at Docklands Stadium on Saturday after his deputies Kurtley Beale and James O'Connor made a number of costly misses at Lang Park.
In a game featuring only a solitary try, Lealiifano traded penalty goals with fullback Leigh Halfpenny, the Welshmen kicking the Lions to a 15-9 lead that remained into the final minutes.
Adam Ashley-Cooper's 77th-minute try put the Wallabies within a point, leaving Lealiifano a hairy conversion kick from near the left touchline to edge his side a point ahead.
Under enormous pressure, and with Beale's missed kick to win the match for the Wallabies in Brisbane fresh in the minds of a record crowd of more than 56,000, Lealiifano struck truly, the ball bending back to sail through the posts.
In a blockbuster finish, Halfpenny was awarded a penalty after the siren from the halfway line, but the laser-sharp Welshman's kick fell short to spark jubilation among the Wallabies, who levelled the series 1-1, with the decider to come in Sydney next week.
"I've seen him kick them from there before. He just didn't strike that one well enough," Lions coach Warren Gatland told reporters.
"Just, you know, a chance to be a hero in that moment ... unfortunately he hasn't hit it quite as well as he's capable of doing."
Versatile ACT Brumbies back Lealiifano, whose potential has long been noted but frustrated by a series of injuries, had finally had his "debut" after a number of false starts, Australia coach Robbie Deans said.
"He's class. Remarkable on his 'debut'," the New Zealander added. "Because it was his 'debut'. To deal with that sort of pressure as calmly as he did, he's clearly got a big future."
Israel Folau, another Wallabies back expected to do big things, failed to score a try in his second test in something of a let-down for an Australian public thrilled by the rugby league convert's stunning two-try debut in Brisbane.
But the explosive winger was threatening throughout in his second test, dominating aerial contests and making a number of line-breaks to trouble the Lions defence.
"He did very well. He offered himself up at the end there. He really took initiative, injected himself in the game and got us over the gain line at a critical time," Deans said.
"That's the sort of great thing we're looking for from him. He didn't wait out on the end and wait for others to serve him. He went looking for it and made a difference for his mates. It was good."
- Sports & Recreation
- Leigh Halfpenny
- Kurtley Beale