The cat called Hugo was found hanged from a bridge on the M62 westbound near junction 33 at Ferrybridge.
Police alerted the RSPCA and one of the charity's inspector's attended the scene at around 12pm on Sunday September 30.
RSPCA inspector Thomas Hutton, said: "Shockingly, I believe Hugo probably was alive when he was hanged.
"He had trauma to his neck and there were no other obvious physical injuries. He was clearly a healthy cat a day before.
"It's very difficult to imagine how anyone could do such a sadistic thing and I’m urging anyone who has any specific information at all to get in touch.
“We have had some information come in, but we need more.Think about this cat, this owner, and what it would be like if this was your pet.
Inspector Hutton added: “He was microchipped and I had the awful task of calling his owner to tell her what had happened. Naturally she was devastated.”
Speaking earlier this month, owner Lorna Taylor said: “I last saw him on Saturday night. I was pulling sticky buds out of his fur.
“I had only had him for a short time but it’s absolutely devastating to think about what has happened to him.
“He was a very bold cat and he would have fought his corner. Whoever did this must be covered in scratches.”
Inspector Hutton said: "It is thought the incident must have happened some time between about 9pm on Saturday September 29 and 10.15am on Sunday September 30.
"Please call the RSPCA appeal line on 0300 123 8018 and ask to leave a message for me.”