Faithful customers questioned the move, with one admitting they would have to "rethink my whole meal".
"The fact that you are replacing lettuce with cabbage makes me rethink my whole meal at KFC. There's four or five other things I would eat before cabbage. It's such a weird choice," one person tweeted.
"Feels like a sign of the apocalypse," said another.
Global news outlets have also taken notice of the hairy predicament Down Under. US news outlet CNN and its syndicated European branches tweeted about the shortages, attracting several comments from sympathetic followers.
The Malaysian Reserve reported Aussies were "clucking mad" over the lettuce-cabbage switch.
Those who don't want cabbage on their Zinger can customise their chosen product and remove lettuce from the recipe.
"We've hit a bit of an Iceberg and are currently experiencing some lettuce supply chain disruptions," KFC said on its website.
"We're working with our multiple suppliers to provide them with support, but we do expect disruptions to continue in the coming days.
"Apologies for any inconvenience caused. We appreciate you all being Little Gems as we work to get things back to normal ASAP."
Since the floods, grocery prices in Australia have increased as one woman saw a single iceberg lettuce costing A$12 and a punnet of blueberries seen at A$20 in a Queensland IGA supermarket.
Supermarket chain Woolworths provided its customers with a seasonal update, advising them it was also experiencing a slight disruption with some vegetables including lebanese cucumbers, kale, fresh herbs, zucchini, beans, tomatoes, capsicum, berries, broccoli and spinach.
"We're still seeing sporadic supply across kale, silverbeet and Asian veg due to the QLD and NSW floods – this should improve over the coming weeks," the website reads.
