In 1917, at the request of the Catholic people in the Mars area, a mission church was established. The first Mass was celebrated by Fr. Timothy O'Shea on March 18, 1917, in Robertson's Hall. Fifty-two adults and thirty-three children attended. The area was first served by the Confraternity of Christian Doctrine under the direction of Fr. Dan Lawless, assisted by Fr. Victor Majka and Fr. Edward Heinrich.

In the spring of 1920 the congregation purchased an abandoned Free Methodist Church. The building was renovated and repaired and was dedicated on December 5, 1920. This same building, remodeled and repaired many times, and now enlarged, still serves as St. Kilian Church. However, the parish was still served by the Confraternity of Christian Doctrine until August of 1924 when the first resident pastor arrived in the parish, Rev. A. J. Weisenberger. At that time the parish was comprised of Mars, Bakerstown, Gibsonia, Cooperstown, Callery and Bairdford areas.

Fr. Weisenberger was followed by Fathers, A.C. Angel, J.B. Keating, G.T. Sheer, Charles Thomas, Fred Seibel, William Schaughnessy, Regis M. Hannon, Charles Schafer, Thomas Harvey, John W. Rebel and presently, Fr. Charles S. Bober.

On July 4, 1934, fire struck the church. Quick work by the local fire department saved the building, although it was heavily damaged. While repair work was done on the church, Masses were held at Mars High School.

The present church hall was started by Father Seibel and completed in 1949 under Father Schaughnessy. The present rectory was built during Fr. Hannon's years at St. Kilian.

Following Vatican Council II, many physical changes within the church became apparent, yet some memories were preserved in unique and meaningful ways. For example, when the altar rail was removed, it was converted into many tiny crosses and distributed to the parishioners as momentos.

The CCD program was established in 1917 with an enrollment of 31 children. St. Kilian's first CCD teachers were Mrs. Margaret Morrison, Mrs. Rosina Weisenberg, and Miss Mary Killian. The CCD buildings were built in the 1970's and one was dedicated to Fr. Schafer.