The lawsuit by Deborah McIlmail contends church officials ignored years of complaints that the Rev. Robert L. Brennan abused her son, Sean, and more than 20 other boys, the Philadelphia Inquirer reported Thursday.
The legal action is her son's "legacy," McIlmail said. "Sean will empower sexual-abuse victims who live in darkness and shame, and consequently bring about the necessary changes for the Catholic Church."
Sean McIlmail died Oct. 13 of an accidental drug overdose at age 26 after telling police Brennan had molested him from ages 11 to 14 beginning in 1998.
His death ended the possibility of prosecuting Brennan, who had been the subject of two grand jury reports on priests in the archdiocese molesting minors. Brennan was not criminally charged because the statute of limitations had expired on the alleged incidents.
McIlmail's allegations had revived the chance of prosecuting the priest. In September, the District Attorney's office charged Brennan with rape and other offenses.
Brennan, 75, now lives in Maryland. He retired after the archdiocese relieved him of his priestly duties in 2005.