[1] The Passionists first assigned Tiedemann as parochial vicar at Immaculate Conception Parish in Queens, New York.

In 1982, Tiedemann left Immaculate Conception to work at St. Joseph Parish in Union City, New Jersey, and Blessed Sacrament in Springfield, Massachusetts.

He was consecrated by Archbishop Donald Reece at Saint Paul of the Cross Cathedral in Mandeville, Jamaica on August 6, 2008.

[2] Pope Francis appointed Tiedemann as an auxiliary bishop of Brooklyn on April 29, 2016; he was installed on August 4, 2016.

He also served as the vicar for West Indian, Caribbean, and African-American Catholics[1] Tiedemann submitted his resignation to Pope Francis after reaching his 75th birthday.