Piven quit the revival of David Mamet's "Speed-the-Plow" in December, claiming his doctors advised him to do so because high levels of mercury were found in his blood.
The producers of the play filed a complaint regarding how Piven handled his departure and the matter went before a grievance committee comprised of five members of the Actors' Equity Association and five members of the Broadway League.
The New York Times said the actors' union sided with Piven, finding he did not violate his contractual obligations by leaving the play due to illness. However, the League representatives backed the producers, who said they didn't believe Piven's explanation that he got mercury poisoning from eating too much sushi, and suspected he left the play because he was bored.
Because of the split decision, Piven avoided potential union penalties for his early exit, however, the producers have the right to proceed to arbitration, The Times said.
The "Entourage" Emmy winner tearfully told the newspaper he tried his best to push through his sickness and continue with the play. He also said rumors that he was exhausted from partying and not really ill are untrue.
"At times I was incapable of getting enough oxygen to get my lines out on stage, and sometimes I'd forget where I was in the play," Piven said. "This misconception that I was out partying was wrong."