In the complaint filed Thursday in Los Angeles Superior Court, David Kohan and Jason Mutchnick ask for damages, saying the network and NBC Studios breached contracts and acted in bad faith.
The men, who created the show and wrote many of its episodes, accuse the two companies of failing to shop the show to the highest bidder, colluding instead to keep profits within the NBC family. General Electric owns both companies.
NBC entertainment spokeswoman Rebecca Marks had no comment pending a review of the lawsuit.
Kohan and Mutchnick said the lawsuit stems from the industry-wide trend of media conglomerates buying up independent production studios.
"It used to be that production companies had an economic interest to obtain fair market value for their programs," the lawsuit states. "This is no longer true in the increasingly common case of negotiations between closely related or commonly owned parties."
"Will & Grace," about a New York City interior designer and her best friend, a gay lawyer, has won 12 Emmys since its creation in 1998.
Despite the show's success, the network pressured NBC Studios last year not to increase the fee for its licensing rights, according to the lawsuit.
The lawsuit also contends that during the show's first four seasons, the studio licensed the rights for "financial terms that were insufficient even to cover a reasonable percentage of the series' production costs and which led to extraordinarily large production deficits."