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About Our Parish

Humble Beginnings

Established on May 10, 1971, by the late Cardinal Timothy Manning, then archbishop of Los Angeles, St. Denis Church has been a vibrant and inspirational center of worship and spirituality in the eastern Los Angeles County of the city of Diamond Bar.  Cardinal Manning appointed Fr. Donald W. Potthoff, a native Angeleno and a member of the 1949 ordination class from St. John's Seminary, Camarillo, founding Pastor.  Fr. Potthoff served St. Denis faithfully for the first twenty two years building a Catholic presence in the community of Diamond Bar.  He retired and continued service to St. Denis up until his death in 2012 at the age of 90.  In the beginning, 650 registered families celebrated Mass in a multi-purpose building which served as a Church, Hall and classrooms.  Many Liturgical ministries took their place in the lives of the developing community of St. Denis.  The Church became known for its Outreach to the poor and needy in the neighboring communities and was given special proclamation by the City Council of Pomona on May 21, 1987 for its commitment and concern.

Recognizing that St. Denis had come of age, Fr. Potthoff embarked on a building project, which included the permanent Church, Pastoral Offices and Rectory.  The dream was realized when Mass was celebrated for the first time in the new Church on December 8, 1989.  The Church was formally dedicated by Cardinal Mahony on April 1, the following year.

Growing Through Change

Today, St. Denis has 6,000 registered families and serves over 25,000 parishioners, visitors and organizations in Diamond Bar and surrounding communities of Walnut, Rowland Heights, Pomona, Chino Hills, Brea, La Habra and West Covina.  We celebrate three daily Masses and eight on the weekends.  We offer opportunities for Reconciliation on Fridays and Saturdays and indeed anytime by appointment.  On Fridays we have adoration of the Blessed Sacrament following the 8:00AM Mass and concluding with a Holy Hour at 9:30PM.  We invite you to join us on a regular basis for any of those celebrations.

Looking to the Future

In the last 4 decades, St. Denis has doubled it members each year.  As a center of grace, growth and generosity, parishioners find it a loving and welcoming place. 

Offering the best possible liturgical, spiritual, educational and community environment is our goal.  Our only limitation in meeting our goals is the space we have available now. We have reached the point where a new Parish Center and Hall are the most critical and appropriate solutions for us to meet the spiritual, physical and social needs of our diverse and growing parish family.  The Building on Faith Campaign is underway to respond to the growing needs of our community.

It is an exciting time to be a part of St. Denis Catholic Community. What we are building is not just bricks and mortar, but a legacy of faith for our children and our children's children. Our parish has grown over these years and so have our needs. The current hall is unable to accommodate all of the programs and services we must offer in order to fulfill our Mission Statement. We look forward to new space for: ministries; the Confirmation program; Lifelong Faith Formation; our youth; religious education; storage; evangelization, adult education, bible study; community outreach; and, parish functions and events.



This Church is our heavenly Father's house, a place of solace and grace, so feel at home here.  Enter reverently, pray quietly, sing joyfully, listen attentively, give cheerfully, and come back gladly.  If you are new to our community, WELCOME!  Please register with us.  If you are visiting, please remain a few minutes and get acquainted.

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