Sharing on TikTok, driver Robert said he noticed the discovery while bringing crates of Coles branded three-litre full cream milk into the dairy section of the Bridgewater store.
Taking a closer look at the haul, however, the driver noted that five crates of Woolworths branded three-litre full cream milk were also included in the delivery.
“Woolworths milk at Coles? How come this happens?” asked Robert, who uses the handle robert_niranjan55, on TikTok.
“We are at Coles Bridgewater. I’m doing milk – three-litre full cream milk – and suddenly I got five crates of Woolies full cream milk.
“Just to let you know guys, that Coles and Woolies are two giants of supermarkets in Australia. How can this happen? How can Woolies milk come here at Coles?”
Other TikTok users were amused by the discovery.
“Someone at the milk factory got very confused that morning!” said one.
Added another: “They must all be made at the same place. Someone was a bit tired when they were putting the stickers on the carton!”
A Coles spokesperson told 7NEWS.com.au the supermarket was investigating the incident.
“All cartons are scanned at different points throughout our supply chain and we’ll be following this up with our supplier and Distribution Centre to find out how this product ended up at our store,” the spokesperson said.