The Supreme Court damages claim was made against a man described as the "best friend" of the woman's father.
The woman, now 26, said in court she remembered three specific incidents when she was aged between five and 10, but said she believed there may have been more.
She said the man exposed himself to her at a public swimming pool, had her touch his penis in a wood shed at his home, and indecently assaulted her in a toilet.
The man, who represented himself during the two-day civil trial, denied the allegations.
Justice Stephen Kaye awarded $81,200 damages, including interest.
He said the woman was particularly troubled during her teenage years.
She was affected in her relationships with her mother and domestic partner, and was obsessively and excessively protective of the couple's young daughter. The woman was now receiving counselling.
Her name, and that of the man, have been suppressed to prevent her identification.
Justice Kaye said the man denied having exposed himself to children, or anyone else, then admitted during cross-examination that he pleaded guilty to two counts of wilful and indecent exposure in a separate case in 1997.
When it was explained to the man that the conviction was relevant when his truthfulness, and the credibility of part of his evidence, was being considered, he replied: "I've sort of got myself snookered, so to speak."
Justice Kaye said the man's conduct towards the woman was particularly outrageous.
"On more than one occasion, he sexually assaulted a young child who was entirely helpless to resist," he said.
"His conduct was calculated to produce significant long-term injury to the plaintiff. It destroyed and violated the innocence of her childhood."
Justice Kaye said evidence given by the woman's mother showed that she believed she had failed her daughter.
The daughter had described the man as getting "rude" in the pool, but the mother told her not to make such accusations because she could get people into trouble.
The mother had later told police her daughter did not want to speak with them.
On one occasion, the daughter was about eight when she saw a "dob in a pedophile" advertisement on television. She told her mother: "I could dob in [the defendant] if you would let me." The mother said she wanted to speak with the child's father about it.
Legal costs today were also awarded against the defendant.