The Good Wife actress hired D/F Management in 2009, later landing her role in the Emmy-winning show and a spokesperson deal with L'Oreal.
She was sued by the company for leaving in 2011, with claims that she owed 10% from her two jobs.
According to WENN, D/F Management is demanding that Margulies pay $420,000 (£262,303) in back payments, as well as a portion of her wages from now on.
However, Margulies has now launched a countersuit accusing the company of failing to provide a written agreement establishing the deal.
In the suit, filed at the Los Angeles Superior Court, the actress is seeking damages for breach of oral contract.