The little grey Staffie, now named Misty, was dumped at RSPCA Woodside Animal Centre, in Leicester.
Misty looked gaunt and also had been left with cuts on her nose, and her skin is in a bad state.
A spokesman for the animal charity said: “She was stood with her head pushed through the bars of the gate, her ears back with these big, brown puppy dog eyes.
The dog was left outside an RSPCA rescue centre
“She just looked so sad and frightened, it was heartbreaking.
“She’s doing okay in kennels but feels really sorry for herself, which is understanding.
“She must be so confused and disorientated.”
RSPCA inspector Karl Marston is now investigating what happened to the poor pooch, and hopes to bring the offenders to justice.
He said: “Poor Misty was skinny and her ribs were clearly visible.