Parental influence and online gaming are blamed as key factors for nearly a third of NSW youth.
A government gambling study of children ages 12-17 has resulted in an educational program aimed at both parents and their children.
A survey of more than 500 NSW children last year found that 29.8 percent had played, some were only 11 years old.
Informal private betting was the most common, followed by scratches and lotteries.
Significantly, few of them played alone.
"Gambling is usually with a parent or other adult relative," said Natalie Wright, director of the Responsible Gaming Bureau.
"The study found that parents had the greatest influence on teenage gambling, so we need to educate both adults and young people."
While 53.7 percent of underage games of chance took place with parents or legal guardians, only 9.1 percent happened alone.
Another key finding from the survey was that around 40 percent of the teenagers in the study had played a video game or app with gambling components.
The study found that gaming and gambling are growing together in online products.
"These games, which mimic real gambling, are potentially gateways to traditional gambling for young people," said Ms. Wright.
She added that while underage gambling is illegal, 21 percent of the children in the study said they poke at lotteries, scratchies, keno, and sports and horse races.
Australian Associated Press