Leslie Moonves, the former chief executive of CBS, plans to fight a decision by the company’s board that denied him a $120 million severance payment after he was fired for cause following numerous allegations of sexual misconduct.

Mr. Moonves, 69, told CBS that he was demanding an arbitration hearing, according to a securities filing on Wednesday. His termination agreement gives him that right, and he had up to 30 days after his Dec. 17 firing to challenge the board’s decision to not pay him the severance.

Under the terms of his termination agreement, CBS has been paying Mr. Moonves’s legal fees, making it easier for him to challenge the board through an arbitration hearing. The process could end up costing CBS as much as $50 million in lawyers’ fees. But should CBS prevail, Mr. Moonves would have to foot the bill himself.

The details of the arbitration hearing will remain confidential, and any decision will be binding, according to the terms of Mr. Moonves’s separation agreement.