The luxury tableware company collapsed into administration last month. Last week production was stopped and administrator Deloitte announced 480 job cuts.
On Sunday, Irish Tourism Minister Martin Cullen, who represents Waterford in Ireland's parliament, said: "My understanding is that before midnight last night [Clarion Capital] launched a substantial bid for the company."
It is thought Clarion is acting with Waterford Crystal’s former chief executive John Foley, who stepped down in January.
Around 200 employees are holding a sit-in in the plant in protest and say they will not move until Deloitte reverses its decision over the job cuts.