More than 600 care workers were dismissed and re-hired on lower pay after the Cornwall County Council-run homes were transferred last April to the Cornwall Care Ltd charity.
Cornwall Care dismissed the workers from their original contracts last September, re-hiring them on new ones. But 249 went to an industrial tribunal in Truro and successfully claimed unfair dismissal.
It is understood that all the care workers employed at the homes will be in line for back pay and the 249 applicants are also in line for compensation.
Chief executive of Cornwall Care, James Robinson, said it faced a "dire situation". The tribunal decision could cause the company to fail "in a comparatively short space of time".
If it could not carry on, the homes must close and the 600 residents would have to be found alternative accommodation, he said. "We are hoping some common sense will prevail from the union," said Mr Robinson, adding that the company board would be meeting as a matter of urgency.
The company was now saying the union should find ways of saving jobs, not destroying them, he said. Unison regional officer Stuart Roden said it was "delighted" by the decision, adding that the workers had been "put through hell".