Police launched an investigation after the blades were discovered concealed inside a tennis ball in Stockport on Friday evening.
Puppies discovered the ball in the reeds in Lyme Park, raising concern that man’s best friend is under threat.
The unnamed dog owner witnessed the brand new blade wedged inside the old tennis ball as his hound began to chew on it.
A post detailing the incident was shared on the Stockport Crime Watch Facebook page.
It said: “It has been doctored by someone who evidently has malevolent intentions towards dogs.
“My puppies carried it back to the car and chewed it up. We found this vicious razor blade inside.
“The pond life responsible may use poison or there may be more doctored balls in the vicinity.”
The worrying incident was reported to police and rangers at Lyme Park.
A spokeswoman for National Trust, which runs the park, told Manchester Evening News: “We are aware of an incident reported by a local dog walker on Friday 24 May.
“The matter is now being investigated by local police.
“We’ve informed our countryside team who will be carrying out additional checks whilst working in the wider estate”.
Lyme Park is home to a mansion estate house which is is the largest in Cheshire was forced to close due to a fire last month.