Peter Nowak alleges that his firing violates a contract guarantee through 2015.
Nowak, of Naples, Fla., was fired last month after a 2-7-2 start that had the Union in ninth place in the 10-team Eastern Conference standings. The Major League Soccer club, under interim coach John Hackworth, remained in ninth place Thursday with a 6-10-2 record.
The club's termination letter alleges that Nowak created a hostile work environment, berating and intimidating other employees, and risked his players' safety by making them play while injured. The letter also accuses him of physical confrontations with players and officials; subjecting players to hazing; and insubordination to the club's chief executive officer.
The termination letter, filed with the lawsuit, also asked him to repay a $46,000 marketing advance.
Nowak seeks at least $150,000 from the federal lawsuit, filed last week in Philadelphia. According to the lawsuit, he rejected a separation agreement that would have paid him through the end of 2012.
The lawsuit names two corporate owners, Pennsylvania Professional Soccer LLC and Keystone Sports and Entertainment LLC, as defendants.
The Union did not immediately return a message left Thursday with its media office.
Nowak, who was hired in 2009, alleges in the lawsuit that the contract called for him to be warned about any deficiencies and be given time to cure them but that he instead was dismissed without warning.