Hong Chi Xiao, 56, was charged with manslaughter over the boy's death, with the Crown arguing Xiao owed the boy a duty of care which he breached through gross negligence.
On Friday, a jury found him guilty following a trial in the NSW District Court.
Xiao initially faced trial last year, but those proceedings were aborted after he sacked his legal team. The boy's mother, father and maternal grandmother were also accused of manslaughter in a trial last year; all three were found not guilty.
Xiao's first trial heard he taught "paida lajin" workshops, a type of slapping and stretching, as a form of Chinese alternative medicine.
The court was told he claimed in a seminar the day before the Sydney workshop that the paida lajin method "unlocked the body's self-healing power", which could cure diseases including type 1 and type 2 diabetes, cancer and Parkinson's disease.
"He told the audience that in respect of insulin, it could be generated by slapping and stretching," Crown prosecutor Sharon Harris said last year. "There was no alternative to insulin. It was insulin keeping [the boy] alive."
The boy's parents enrolled him in Xiao's workshop with the hope of "curing" his diabetes, because he was tired of being injected with insulin four times a day. As part of the workshop he was made to fast for three days, before he was finally allowed to eat again on the day he died.
The first trial heard Xiao told the boy's mother that she should not give him any more insulin, because "medicine is poison, Western medicine cannot cure you".
As the boy's health deteriorated and he started vomiting, Xiao told the boy's mother that toxins were being released from his body and it was a positive sign, not a negative one, the court was told.
Xiao denied making such comments.
He will return to court on Friday for a sentencing date to be set.
Earlier this month a court in England issued a warrant for Xiao's arrest over the alleged gross negligence manslaughter of a woman who attended one of his workshops in 2016. The woman's son told British media the 71-year-old also had diabetes and attended a week-long workshop in England's south-west in an attempt to "cure" the condition.
British police said they will "work with the relevant agencies" to have Xiao stand trial over the woman's death.
Georgina Mitchell is a court reporter for The Sydney Morning Herald.