The juvenile snake was spotted in a lid as the woman packed school lunches in Adelaide, according to reptile handler Rolly Burrell.
Mr Burrell said he advised her to close the box and take it outside, after the woman had called him for assistance.
He identified the reptile as an eastern brown, one of the world's most venomous snakes.
"Not really what you expect to see when you check if [your] child ate their fruit," Mr Burrell wrote on Facebook.
He said the snake was removed without incident.
Mr Burrell said even juvenile snakes had dangerous venom.
"It is very lucky that she spotted the snake... a little kid would not even feel the bite from something so small," he told the BBC.
The snake catcher said he suspected the reptile had headed for the pantry because it was "one of the darkest spots in the house".
The species is found along coastal and inland areas of mainland Australia. It has been responsible for 23 deaths since 2000, a study of coroner's data found last year.