"Taylor Swift has put money before compassion by agreeing to perform at the 2019 Melbourne Cup," the group posted.
"Horses are being killed for gambling profits and entertainment. If Taylor Swift cares at all about other animals the way she appears to care about cats, she will cancel her show and make a strong statement that animal abuse is unacceptable.
"Head on over to Twitter and politely ask @TaylorSwift13 to say #NupToTheCup," it read.
Swift had expressed her excitement over the big event in a statement published in the Herald Sun today.
"I can't wait to come to Melbourne, and I can't wait to come to the Melbourne Cup," she said "I've heard so much about the race."
It will be her only Australian performance.
The announcement follows a report in the Herald Sun last month that race officials were in talks to secure either Swift, Shawn Mendes or Camila Cabello to perform on the big day.
So far, the Facebook post by the non-profit organisation has been inundated with comments from people expressing their disappointed over Swift's decision.
"I thought she was an animal lover? What a hypocrite," one user said, while others said they had messaged the star on Instagram urging her to cancel.
On Twitter, fans have begged the star to call it off:
