A member of the public spotted the injured man near a Darwin beach in the Northern Territory on Monday night and phoned police.
Police arrived to find the 45-year-old man with a lot of blood on his head.
The man said he was fishing with a friend when he tried to reel in his catch but the catfish flew up and struck him.
"The impact caused the venomous back spine of the fish to lodge into the side of his head," Duty Superintendent Louise Jorgensen said in a statement.
"He writhed in pain and bled profusely while his friend calmly took possession of the prize catch," she said.
"Remember folks, its Northern Territory Water Safety Week - be careful out there."
An Australian man has been left bloodied and embarrassed after being hit in the face by a catfish.