Sister Mary Denise Diethrich, SC


Sister Mary Denise Diethrich, SC, age 90, died at Caritas Christi, the motherhouse of the Sisters of Charity of Seton Hill in Greensburg, on May 8, 2022. A native of Altoona, PA, Sister Mary Denise entered the congregation of the Sisters of Charity on September 8, 1949, from Saint Therese of the Child Jesus Parish in Altoona.

Preceded in death by her parents, Eustace M. and Mary Martina (Cusick) Diethrich, two sisters, Mrs. Lois (Walter) Sanker and Mrs. Ann (Kennet) White, and a maternal aunt, Sister Mary Stephen Cusick, SC. She is survived by one sister, Mrs. Mary Clendenning, and many nieces and nephews. She interacted and traveled with many of her nieces and nephews throughout her life, many who in return supported and visited her in her retirement years at Caritas Christi.

She earned a bachelor’s degree in education from Seton Hill University and a master’s degree in reading and language arts from the University of Pittsburgh. Sister Mary Denise ministered in a variety of educational ministries including teacher, principal, supervisor and religious education consultant. She taught students of the middle school level in schools of the dioceses of Greensburg and Pittsburgh and the Archdiocese of Washington.

As principal of Holy Rosary School in Juniata in the early 1960s, Sister Mary Denise directed the establishment of the first non-graded school in the Diocese of Altoona-Johnstown. She was named principal of the Greensburg Catholic Middle School from 1968 until 1970.

After a sabbatical year, 1984 to 1985, at Gonzaga University in Spokane, Washington, she was assigned the principalship at Saint Catherine School in Phoenix and then ministered as assistant principal at Our Lady of Perpetual Help School in Scottsdale, Arizona. From 1990 until 1992, Sister Mary Denise was a pastoral associate at Christ the King Parish in Memphis, Tennessee. In 1992, Silver Burdett Ginn Publishing, Inc. recognized her competence, and enlisted Sister Mary Denise to plan, coordinate and teach at national catechetical workshops. From 1996 until 1999, she ministered as the firm’s director of catechetics. Sister Mary Denise was the director of religious education in the Diocese of Wheeling-Charleston from 1990 until 2001. From 2001until 2005, she ministered as the faith formation director at LaPurisima Concepcion Parish in Lompoc, California.

In 2005, the Sisters of Charity asked Sister Mary Denise to collaborate with the Seton Hill University Art Program to create the Seton Arts Service Corps, an endeavor to develop a concept of service, in light of the Vincentian-Setonian tradition, and to understand the potential for service to communities through the arts. An author of several articles for the Catechist magazine and co-author of Study Skills for Elementary Schools, Sister Mary Denise received certificates of recognition for outstanding catechetical presentations in Japan, Korea and Germany. She was also recognized for her outstanding service at a home for abused girls in Phoenix, Arizona. She was a volunteer at Rendu Services and at the Literacy Council of America.

In reflecting on her life as a Sister of Charity, Sister Mary Denise said, “From the day I entered I have loved being a Sister of Charity. I am so grateful for the numerous opportunities I have had to use my formation, my education and my experience to serve others.”


Visitation: Wednesday, May 11 3 – 7 PM
Vigil: Wednesday, May 11 7 PM
Funeral: Thursday May 12 10:30 AM
Caritas Christi Motherhouse, DePaul Center Road, Greensburg, PA 15601

The funeral liturgy will be live-streamed; access through the link:

Memorial contributions may be made to the Sisters of Charity, De Paul Center, 144 DePaul Center Road, Greensburg, PA 15601. For more information visit the website,