Best friends Bonnie and Clyde were brought to the animal shelter in Norfolk after they were found wandering the streets in a rain storm.
When the pair are together Clyde, five, seems as capable as a fully sighted dog – but he won't move unless Bonnie, two, is close.
Bonnie guides him on walks or towards food and lets him rest on her when he becomes disorientated.
Cherie Cootes, who runs the Meadown Green Dog Rescue Centre in Loddon, Norfolk, said: "He totally relies on her the whole time. When she walks she tends to stop and make sure he's there – she does look out for him."
Vicky Bell, a spokeswoman for Guide Dogs for the Blind Association, said she had never heard of a dog voluntarily acting as a guide for another dog.
"There's absolutely no option of homing them separately – they have to go as a pair," she said. "This is a very unusual case – it's such a lovely story.
"Some dogs take to guiding better than others because they naturally have the right temperament."