The 42-year-old was tearful as he performed through the rain to the 55,000-strong crowd on Friday for the first time since his son Noah, 4, was diagnosed with stomach cancer in November 2016.
Buble invited his recovering son on stage during the finale of his set and told fans there were "many moments" he thought he "might not come back" to showbiz.
The headline performance was the first he had planned since he and actress wife Luisana Lopilato announced that their eldest son had been diagnosed with the disease at the age of three.
"You have no idea how much it means to be to be surrounded by all you beautiful souls," he told his fans.
"I want to thank you for everything you have done for me. Thank you from me and my family for your love and support."
The crowd burst into applause when Buble embraced his son with a huge hug and a kiss.
Buble danced and slid his way around the drenched stage during the heavy downpour and thunderstorm, proving his two-year break hadn't affected his stage presence.
He opened with Feeling Good as he told the crowd that the weather was "just as I imagined it would be".
The singer also poked fun at the political climate when introducing the brass section of his band from the US, joking: "Don't blame them".
He encouraged fans to "snuggle up" and enjoy the music despite "culturally what's going on right now".
After closing the set with a moving rendition of You Were Always On My Mind, he wiped away tears and carried his son off stage.
At the time of Noah's diagnosis, Buble and his wife said they were "devastated" and were suspending work commitments to devote their time to taking care of him.
He has since made a full recovery and in April Lopilato said the couple remained hopeful and were "looking forward to thinking about the future" and seeing their children grow.