Almost 1000 mourners congregated in colour at Beaumaris Secondary College on Monday afternoon.
Bowles and her best friend Bianca Jones had been holidaying in Laos when they became unwell after consuming drinks in the tourist town of Vang Vieng.
Bowles died in a Bangkok hospital on November 22, a day after Ms Jones died in another hospital in the Thai capital.
Acting Principal at Beaumaris Secondary College, Peter Bartlett, thanked people across Australia for their "love, support and compassion".
"Today is a profoundly significant day for our family as we come together to celebrate Holly's life," Mr Bartlett said in a statement on behalf of the Bowles' family before the service.
"Holly was loved and adored by so many people, and today is a reflection on her life, however she will remain forever in our hearts."
Both women's families have asked people to donate to the girls' GoFundMe in lieu of flowers.
The fundraiser has received more than $400,000 and was to help with the families' financial burdens before being expanded to help raise awareness about the dangers of methanol poisoning.