Samuel Ian Paterson, 24, made the plea as he faced court on Friday, four months after his three-year-old son Caden died at a police station from head injuries.
Paterson and the boy's mother, Aneshia Daisy Case, 23, have both been charged with manslaughter and drug trafficking following Caden's death.
Their son was critically injured after the family's white Mazda veered off the road and crashed in bushland north of the Gold Coast on October 25.
A witness saw the car swerve off the road and rushed the mother and Caden to Beenleigh Police Station.
Officers at the station attempted CPR but the boy couldn't be saved, police said.
Paterson fled the accident scene and was later found at a nearby address with a one-year-old boy who was uninjured in the crash.
After months of investigation, both parents were charged with manslaughter and appeared in Brisbane Magistrates Court on Friday.
Paterson has been in custody since the accident after facing separate charges.
Appearing via video link on the fresh manslaughter and drug trafficking charges, Paterson appeared unsure when asked whether he would need to seek legal aid, with the case adjourned until March 30.
"I need to talk to my mum," he told the court.
"I was going to probably pay for a lawyer."
The manslaughter charge against Case was mentioned separately in the Brisbane court on Friday.
Case - who is also charged with unlicensed driving - did not appear for the brief mention.
Her matter was remanded until Monday and the young mother was ordered to appear.
Police will allege Case was behind the wheel at the time of the accident, but have refused to comment on the cause of the fatal crash.
Detective Acting Inspector Kent Ellis said the investigation was "extremely complex" and involved a forensic reconstruction of the crash and analysis of physical evidence and CCTV footage.
"Determining who was driving at the time of impact required an extensive amount of investigative work," he said on Friday.
"Extensive forensic and mechanical investigations, analysis of physical evidence, extensive analysis of CCTV, digital and additional intelligence enquiries."
Police earlier alleged the mother and children had travelled from the Gold Coast to collect the father from a Beenleigh address before the crash.
The father was separately charged with domestic violence offences in October, when his emotional family claimed he would never harm his children.
"We are sick of the f***ing lies," the boy's grandfather yelled at the media after the father's appearance at Southport Magistrates Court in October.
"He loves his kids ... he was trying to protect them. He would never hurt them."
Family members were not in court as the manslaughter charges were mentioned on Friday.
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