Amanda Camm, Queensland's Minister for Domestic and Family Violence and Child Safety, told reporters the decision to relinquish her post was hers, with Premier David Crisafulli standing alongside her.
"It has been my decision and mine alone," she said.
However, while Ms Camm denied she had been forced to step down, the minister has been under sustained pressure after a series of child safety failures.
The Whitsunday MP returned from six weeks' medical leave last week, having previously spoken of battling chronic migraines.
"I have realised that my recovery still has a way to go, and would not be aided by the position of minister, the ongoing stresses associated with that role, and the workload," she said.
She told reporters the attack on federal MP Helen Haines had also swayed her decision.
Last month, new data showed the number of Queensland children known to child safety who had died had gone up almost 60 per cent in a year.
In June, it was revealed that children in state care were sleeping on mattresses in government offices.
A bungled rollout of a new IT system costing $183 million left child safety officers unable to access vital information, including court orders, for at-risk children.
Ms Camm's personal life also came under scrutiny after her extramarital relationship with Olympics and Paralympics minister Tim Mander became public earlier this year.
It led to Mr Mander briefly stepping down as the Australian Electoral Commission investigated allegations he had broken voter enrolment rules after moving out of his family home when his marriage ended.
The pair insisted they had fulfilled their obligations to report any conflicts of interest and adhered to the parliamentary code of conduct.
The opposition has repeatedly called for Ms Camm to be sacked.
In a statement, Ms Camm said she had been part of delivering nation-leading domestic and family violence laws.
"Doubling the calls answered on DVConnect so victims can get the support they need, when they need it, is something I'm proud to have delivered," she said.
However, domestic and family violence was cut by $38.5 in the state budget.
While Ms Camm will remain as the MP for Whitsunday in north Queensland, she refused to commit to recontesting the seat at the next election, saying she was focused on her health.
"It became apparent to me that I came back too early," she said.
"I don't get second chances with my health."
Mr Crisafulli said an announcement in regard to Ms Camm's replacement would be made shortly, avoiding a cabinet reshuffle.
He said Ms Camm had inherited a "broken system", denying he had forced her to step aside.
Opposition leader Steven Miles slammed the premier for not acting sooner.
"It's incredible to me that David Crisafulli is pretending that there is nothing wrong," he said.
"If ever there was a day for him to put aside the spin and acknowledge the failures of his government in child safety, it should have been today."
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