The tourists rode their luck late on to win the opening Test 23-21 against the Wallabies in Brisbane on Saturday to take a 1-0 lead in the series.
The Ireland back row admits that he has been amazed by the travelling support so far on the summer tour.
"It was an amazing occasion. Even the night before the Test walking around Brisbane there were people doing choir practice outside. They were breaking into different songs and then breaking into 'Lions, Lions' - it was amazing," said Heaslip.
"There have been a lot of big games against Australia that spring to mind, like in the 2011 World Cup. That felt like a home game.
"But when we ran out we saw a lot of yellow and then patches of red, but by God were they vocal. When we went to the well they were screaming and we could hear them chanting 'Lions, Lions' - it took your breath away at times."
The Lions face the Melbourne Rebels on Tuesday.