[1][5] Deciding to become a priest, Keeler entered St. Charles Borromeo Seminary in Wynnewood, Pennsylvania, receiving a Bachelor of Arts in 1952.

With the start of the first session of the Second Vatican Council, Keeler served as peritus (expert) and secretary to Bishop George L. Leech in Rome.

As bishop of Harrisburg, Keeler served on committees for interreligious dialogue and helped expand diocesan youth ministry.

[13][8] In 1993, Dontee D. Stokes reported to the archdiocese that he had been fondled over a three year period as a minor by Reverend Maurice Blackwell, pastor of St. Edward Parish in West Baltimore.

[19] At that time, journalist Bill Broadway of The Washington Post called Keeler "one of the most respected Catholic leaders in the United States.

"[3] John Paul II created Keeler as cardinal-priest of Santa Maria degli Angeli e dei Martiri in a consistory on November 26, 1994.

[20] That same year, the pope named him a member of the Pontifical Council for Promoting Christian Unity and the Congregation for the Oriental Churches.

[6] Keeler participated in the 2005 conclave in Rome that elected Cardinal Joseph Ratzinger as Pope Benedict XVI.

"[17] Keeler, however, became the first bishop to identify publicly priests who had been "credibly accused of child abuse," listing 57 on the archdiocese website and detailing $5.6 million spent on settlements, legal fees and counseling.

'"I think Cardinal Keeler has taken a very bold and courageous and pastorally sensitive approach," said Bishop Wilton Gregory, President of the USCCB, at the time.

[22] Keeler was responsible for the restoration of Baltimore's Basilica of the National Shrine of the Assumption of the Blessed Virgin Mary, America's first cathedral.

[26][27] On August 14, 2018, the Pennsylvania Supreme Court released a report that alleged Keeler committed criminal inaction during his time as bishop of Harrisburg.

[28] The grand jury report stated that Keeler learned in 1987 of allegations of sexual abuse against Father Arthur Long.

[29] Immediately after the release of the Pennsylvania grand jury report, the Archdiocese of Baltimore in August 2018 cancelled plans to name a new Catholic school after Keeler due to his handling of the Long accusations.

[2] However, Jewish leaders threatened to boycott the Miami meeting because John Paul II had recently met with former U.N. Secretary-General Kurt Waldheim.