Edgar Bronfman Jr., the head of Warner Music, yesterday sued his former employer, Vivendi SA, alleging the entertainment conglomerate he helped form broke its contract by reducing his pension payments.

Attorneys for Mr. Bronfman, the billionaire scion of one of North America’s richest families, say in legal papers filed in Manhattan Federal Court that Vivendi deflated his pension checks by 65% after claiming to discover “an alleged ‘mistake’ in the calculation” and “erroneously crediting” him for 15 years of service beyond the 20 years he had accrued.

“There was no mistake,” the papers say, adding that the additional years were part of agreements Mr. Bronfman reached with Vivendi. They ask a federal judge to award him unspecified damages, with interest.

In addition to business investing, Mr. Bronfman and his family are prominent philanthropists, with interests ranging from developing nations to Jewish causes. He heads the board of directors of the nonprofit group Endeavor, an international development organization that supports entrepreneurs in emerging markets.

Mr. Bronfman had been chief executive officer of Seagram when it merged with the French firm Vivendi in 2000. After the merger, he became the new company’s executive vice chairman, serving as a consultant, shareholder, and board member until December 2003, the court papers say.

Most recently, Mr. Bronfman has been Warner Music’s chairman. Before selling Seagram to Vivendi, he transformed the liquor distributor into the world’s largest music company. At Warner, his bet that digital-age music sales would spur growth has yet to pay off.

An attorney for Mr. Brofman, Charles Michael of Sullivan & Cromwell, declined to comment on the case, and a corporate spokeswoman for Vivendi, Flavie Lemarchand Wood, did not immediately return a phone call seeking comment.