Louis Francesco Rapisarda, 33, on Friday pleaded guilty in Brisbane Magistrates Court to disturbing the peace at a place of worship and creating a public nuisance over the incident on May 10.
The court was told Rapisarda first drove past the Mitchelton Presbyterian Church and shouted "Allahu Akbar" at people gathered outside.
He then drove to the Masjid Taqwa mosque at Bald Hills, north Brisbane, walked into the mosque and again shouted "Allahu Akbar".
He told worshippers: "I've got an AK-47 strapped to my back".
Worshippers called police and officers arrested him soon after.
No weapon was found and no one was physically injured.
Defence lawyer Daniel Hannay said Rapisarda had faced mental health problems since his father died by suicide when he was 16.
Rapisarda had been treated for bipolar disorder but was not taking his prescribed medication at the time of the incident, triggering manic episodes, Mr Hannay said outside court.
"He has a history of mental health issues and has been diagnosed with bipolar disorder," Mr Hannay told AAP.
"He was off his medications at the time and there was a clear link between his manic episode and his bipolar disorder."
Rapisarda wrote a letter of apology to the mosque, expressing deep remorse for his actions.
"He was emotionally distraught during the police record of interview - he broke down in tears and kept apologising, saying he didn't know what was going on," Mr Hannay said.
"He's obviously apologetic, he wants to move on and he apologises to all the parties involved."
Citing his submissions to the court, Mr Hannay said his client told police: "I'm not a racist, I was just off my meds".
Rapisarda had a long work history, a mortgage, was in a stable relationship and there was little chance of him reoffending, Mr Hannay said.
The court ordered Rapisarda to complete 60 hours of community service and no conviction was recorded.
Muslim peak bodies spoke out about the "frightening" incident, with the Australian Federation of Islamic Councils saying it should not be dismissed as random.
The councils' president Rateb Jneid warned anti-Muslim hatred was shifting from online abuse into "physical threats, arson, intimidation and alleged acts of planned violence".
The Australian National Imams Council called the alleged threats a "grave violation" of the safety and sanctity of a place of worship, and warned of the "increasing normalisation of anti-Muslim sentiment".
The Masjid Taqwa mosque was also targeted in December when vandals sprayed a swastika and anti-Muslim graffiti on an outside wall.
Local Labor MP Bisma Asif said a place of worship should be "a place of peace" and no one, regardless of faith, should fear for their safety when they gather to pray.
She said the rise in racism, Islamophobia and anti-Semitism had been fuelled by politicians using racial division to win votes and by those "too weak to call it out".
Police said they treated all threats against cultural and religious communities very seriously and urged anyone who felt afraid to contact authorities.
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