Donna Sim, from Townsville in the state of Queensland, gave her toddler a plastic container when he was playing in the garden a few weeks ago.
Kyle Cummings put some eggs he had found inside the box and left it in the warm confines of his wardrobe.
But when Ms Sim opened the wardrobe she got the fright of her life, seeing seven baby snakes writhing around inside.
The reptiles, later identified to be eastern brown snakes, are regarded as the world's second deadliest species behind the inland taipan.
Fortunately, Kyle had clamped the lid of the container down firmly, and the snakes had not yet grown large enough to push it off and escape.
"I was pretty shocked, particularly because I don't like snakes," Ms Sim told the Townsville Bulletin newspaper.
The snakes were handed over to wildlife carers in Townsville.
North Queensland Wildlife Care reptile co-ordinator Trish Prendergast, who released the seven eastern browns, said: "The little boy was extremely lucky he didn't get bitten."
Ms Prendergast said it was illegal to interfere with protected wildlife but the mum and her family would not face any charges.
The reptile co-ordinator said eastern browns were "born killers" and even as babies have enough venom to kill people, although their fangs are very small when they are young.
"If he'd opened the container her might not be here today," she said.
"He's always out in the yard, he always loves playing out there," Kyle's older sister Shannon told the paper.
"He's a real country boy. he was a bit sorry to see them go. He wanted to keep them."
