Jimmy Sullivan, the member for the electorate of Stafford, was found dead at his home. He was 44.
Police responded to a call about 10.15pm on Thursday and found his body at his Stafford unit in Brisbane's north.
His death was not being treated as suspicious.
"Queenslanders will be shocked to hear of the sudden passing of Member for Stafford Jimmy Sullivan,'' Premier David Crisafulli said in a statement.
''On behalf of all Queenslanders, we extend our heartfelt condolences to his family during this difficult time."
His death will trigger a by-election for the Stafford electorate in Brisbane's north.
Mr Sullivan was first elected to parliament as a Labor MP in 2020, following in his father's footsteps.
His dad Terry Sullivan had been a state Labor MP from 1992 to 2006.
Queensland Labor said Mr Sullivan's loss would be felt by many.
"All of us in the Labor family are in shock today at the sudden and tragic passing of our friend and colleague, Jimmy Sullivan," the statement said.
"We honour his memory and his deep connection to his local community where he was born, raised and honoured to serve his whole life.
"Our thoughts are with Jimmy's family, friends and all who loved him."
State opposition leader and former Labor premier Steven Miles issued a brief statement, saying "our thoughts are with Jimmy's family, friends and community this morning as we all process this news''.
Mr Sullivan served as assistant to the Minister for Justice and Veterans Affairs in the Miles government and was previously chief of staff to former attorney-general Yvette D'Ath.
He was re-elected in the 2024 state election, surviving a 5.5 per cent swing against him as the Miles government was swept from power by Mr Crisafulli's Liberal National Party.
He fell out with Labor soon afterwards, with police called to an alleged domestic incident at his home the day after the election.
No charges were laid.
He was placed on leave to attend to medical and legal issues, before being disendorsed by Labor in May 2025, forcing him to the crossbench.
Speaking as an independent in parliament for the first time, Mr Sullivan broke down, telling MPs he was suffering from post-traumatic stress disorder caused by the death of his first daughter.
"I spiralled, I recognise that, and I put my hand up for healthcare," he told parliament.
Mr Miles accused him of failing to adhere to a "safe return to work plan".
On his parliamentary web page, Mr Sullivan described himself as "a local through and through" who had grown up and gone to school in the electorate.
Before politics, he was a lawyer and former judge's associate in the District Court of Queensland.
He worked across government and law reform in Canberra, Brisbane and Washington DC, working in the office of Democratic Senator Ron Wyden.
Police said a report would be prepared for the coroner regarding Mr Sullivan's death.
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