Raban Alou, 18, is charged with aiding and abetting the killing of police accountant Curtis Cheng, 58, on 2 October.
Talal Alameddine, 22, is accused of supplying the weapon used by Mr Cheng's killer, 15-year-old Farhad Jabar.
Neither appeared in court and no applications for bail were made.
Mr Alou's lawyer, Moustafa Kheir, told reporters outside the court that his client would be fighting the charges.
He said his client had been held for more than 200 hours "for the purpose of interrogation" and that the charges against him relied on circumstantial evidence.
Police have alleged that Mr Alou handed the gun to Jabar. They also allege Mr Alameddine supplied the gun to Mr Alou hours before the murder.
The case has been adjourned until 10 December.
Mr Cheng was killed outside police headquarters in the Parramatta area of Sydney and Jabar was then shot dead by police. Officials described it as a terror attack.
More than 200 officers later raided properties in the area.
Jabar, an Australian born in Iran and of Iraqi-Kurdish heritage, is reported to have shouted religious slogans as he killed Mr Cheng.
In the wake of the killing, Australian Prime Minister Malcolm Turnbull called a meeting with security chiefs.
He warned that radicalisation was spreading among the young.
"We are dealing with an evolving threat," he said.
"The shocking murder of Curtis Cheng, the shocking act of terrorism perpetrated by a 15-year-old boy reminds us yet again that radicalisation, extremism can be seen in the very young."
Australia's police chief had earlier warned that the terror threat facing the country was getting worse.

Zaneta Krokova, 11, and Helina Kotlarova, 12, who were "holding hands" as they crossed the road, died after the crash on Ashton Road.
Four men, aged 59, 48, 38 and 18, remain in custody on suspicion of causing death by dangerous driving.
A fifth man, aged 23, has been de-arrested, police said.
Greater Manchester Police (GMP) said he was initially arrested for the same offence but was now assisting police with enquiries.
Greater Manchester Police said it had identified the car involved in the collision as a Blue Peugeot 807.
The dark blue vehicle, which had evidence of previous damage to its rear window, was found abandoned on Honeywell Lane.
Nigel Whittle, principal of Oasis Academy, Oldham, said the school was "deeply saddened" by the news of the deaths of Zaneta, who was a first year student, and her cousin Helina Kotlarova, a former pupil.
He said: "Our thoughts and prayers are with their families and friends at this extremely distressing and difficult time.
"We are a very closely-knit school community.  As our students return following the Christmas break, I know that they will care for one another, and our staff will be available to offer the support and time necessary as we all come to terms with this awful loss."
He said with the agreement of the Krokova family the school would join together to pay tribute to Zaneta in the coming weeks. A book of condolence would be opened on Thursday, he said.
Two men charged in connection with the terrorism-linked shooting of an Australian police worker have been remanded in custody by a Sydney court.
[NEXT_CONCEPT]
Police have been given more time to question four men held over an apparent hit-and-run crash in Oldham on New Year's Eve in which two cousins died.