The boy - who can't be named - was on Wednesday sentenced in Brisbane's Children's Court for offending that occurred over two-and-a-half months in 2023.
The teen accessed, possessed and transmitted materials associated with Islamic State from August to October last year and twice "encouraged others to violence", the court was told.
A handwritten pledge of allegiance to the IS leader was found when police searched the boy's home on October 19 2023.
The court was also told he had researched ways to access weapons.
He was 16 at the time of the offending.
"Your involvement was to disseminate already available material and to participate in online forums and on two occasions, you encouraged others to violence without a specific plan or occasion in mind," Judge Deborah Richards said.
The teen had been exposed to domestic violence and lacked support at home resulting in isolation at school, the court was told.
At the time of the offending, he had erratic sleep patterns, limited contact with family, smoked cannabis and played video games.
Judge Richards accepted a letter from the teen expressing remorse for his actions and noted his willingness to co-operate with youth justice workers while in detention.
"I accept that that's a sincere letter that you really do feel that that time in your life was something that you would take back if you could," she said.
"You've denounced Islamic State and now know the dangers of such activity."
The teen had pleaded guilty to one count of being a member of a terrorist organisation.
He had been in custody for 251 days.
The boy on Wednesday was handed an 18-month probation order with strict conditions including regular sessions with mental health counsellors experienced in dealing with people radicalised in hate groups.
He had undergone a psychological report and intended to live with his mother, the judge heard.
She told the teen that the federal attorney-general may apply for a control order to impose further probation conditions, including potentially monitoring his activity.
1800 RESPECT (1800 737 732)
Lifeline 13 11 14
28°C