Anthony Roper, aged 69, was last seen at around 5pm Friday on a street in Cleveland.
Mr Roper may be disoriented or possibly lost as he suffers from a medical condition.
He was last seen wearing a white shirt with brown stripes, jeans and a blue backpack.
His family are concerned about his whereabouts, as the search continues after more than 24 hours.
Mick Ackery from Queensland Police said the family was desperate to have the man home.
“He has a medical condition which can affect his cognition. That makes him a vulnerable person in our community,” Mr Ackery said.
“He needs his community to get behind him and help bring him home.”
Authorities are asking everyone in the Cleveland areas to check their backyards, sheds and boats in case Anthony is taking shelter there.
Police and SES will continue to search throughout the night in the rain until he is found.