Donna Pritchett was stunned to discover the solitary sprout in her Christmas shop when it was delivered to her door.
The mum-of-two had planned a festive feast for eight people at her home in Aylesbury, Buckinghamshire, of which the tiny green veg plays a vital role.
Donna, 47, who had decided to try online shopping for the first time, was bemused to find just one sprout wrapped in a 4p price sticker, as part of her £130 order.
She says: "When it arrived, my daughters and I thought, 'What on earth are we going to do with one little sprout? How's that going to feed eight of us?'
"That's probably less than a leaf each and we're all big sprout lovers in this family. It was hilarious."
A novice to online shopping, Donna realised she must have accidentally clicked one sprout instead of 1kg of sprouts.
But Sainbury's were quick to come to her aid, sending her a bumper pack of sprouts as well as a bottle of champagne to help spread the festive cheer.
A spokeswoman said: "This kind of thing is very rare but does occasionally sprout up."