Efforts to organize a Catholic congregation in Belle Vernon were made as early as 1905, although at that time there were very few Catholic families in the community. The first Mass in Belle Vernon was held in a small hall in the Edgar Corwin Building, Main Street. The altar for the initial Mass was built by the late Jacob B. Hassen. This attempt proved unsuccessful. A few months later the local Catholics were again attending Mass at Charleroi and Monessen as had been their custom, making the trip to Charleroi on foot.

Between 1908 & 1909, another attempt - this one successful - was made to organize a congregation. Father Albert J. Wigley, then pastor of St. Leonard Church in Monessen, guided the effort and established a St. Sebastian Church as a mission.   Mrs. Drvao, the wife of the superintendent of the former local plant of the American Window Glass Company, was very helpful in setting up the new mission.

Mass was celebrated in an empty room on the second floor of the McClure Building at Second and Main Streets. Later, the congregation moved to the larger Clarence Luce Building but went back to the McClure building when the Luce property owner decided to remodel.

The average attendance at Sunday Mass at this time numbered about 22. The average collection was less than two dollars. House-to-house collections and donations from parishioners at St. Leonard helped to increase the church funds here.

Around 1914 and 1915, serious thought was given to the building of a church and in 1917, the congregation secured property at the corner of Speer and Baltimore Streets. The "old" St. Sebastian Church was built by the Moats Lumber Company at a cost of $5,000 in this fast-developing new section of the community known as North Belle Vernon. The parish still remained a mission to St. Leonard Church. There was but one Mass on Sunday, preceded by confessions and followed by catechism instructions for the children.​

​It was a glorious day for St. Sebastian early in 1924 when the late Most Reverend Hugh C. Boyle, D.D., Bishop of Pittsburgh, assigned Father Dennis N. Murphy as the first resident pastor. He pioneered the development of the new parish during his 12 years in Belle Vernon.

Carmel Valentino Venneri was the first baby baptized in the new church, receiving the Sacrament on August 3, 1924. Mrs. Narchesi Niccolai was the first parishioner buried from St. Sebastian on December 22, 1924. James N. Dunbar and Catherine Elizabeth Shaw were united in Holy Matrimony on May 30, 1925, the first marriage performed here by Father Murphy. The initial First Holy Communion class on July 5, 1925, numbered 30 members. Bishop Boyle administered the Sacrament of Confirmation for the first time at St. Sebastian on May 11, 1926 to 79 members of the congregation. Frank Dayner, who served as committeeman for 29 consecutive years, A.P. Neeson, and Sylvester Welsh were named to the first Church Committee by Father Murphy.

An ever-increasing congregation made necessary the building of a new wing to the church which provided for an additional 135 parishioners. It was during Father Murphy's stay at Belle Vernon that the first St. Sebastian rectory was purchased at the corner of Green and Baltimore Streets. After 12 years as pastor, Father Murphy was transferred to St. Stephen Church in Hazelwood. He was succeeded by the Father James J. O'Connell, who served as pastor until 1942. Many improvements were made in the "old" church during Father O'Connell's successful tenure, including plastering of walls and installation of stained glass windows.

Our third pastor was Fr. Dennis A. Boyle, who served for two years until his death in 1944. While pastor here, he initiated a novena in honor of Our Lady of Victory. Replacing Fr. Boyle was the Father. Eugene Harkins, who found an ever enlarging congregation eager to advance to more spacious accommodations. A need was seen, not only for a larger church but for a much-desired parochial school. Under his leadership the parishioners rallied to the task and the material treasury soon showed evidence of the expansion needs becoming a reality. Property was purchased on Fayette Road but later abandoned in favor of the Broad Avenue site, which was not then available.

Father Francis L. Martin, with instructions from Bishop Boyle and his coadjutor, the Most Reverend John Francis Dearden, came to Belle Vernon in 1949, replacing Father Harkins, who was assigned to an enlarging St. Anne Church in Castle Shannon. Unexpectedly, in 1950, as plans were advancing to begin construction of a church and school, the Diocese of Pittsburgh was divided and the new Diocese of Greensburg was formed. The Monongahela River was more or less the boundary line with Belle Vernon falling under the jurisdiction of the new diocese.   The many perplexing problems in setting up a new diocese brought a delay in the plans for St. Sebastian's expansion.

The need for a larger church became very urgent with the congregation doubling in five years to 850 families. Early in 1954, the building plans were finally drawn up under the guidance of the Most Reverend Hugh L. Lamb, D.D., Bishop of Greensburg, and his Diocesan Building Committee. The present site of the church (Broad Avenue at Fayette Street) was purchased and architect H. Ernest Clark engaged to draw up plans for the new edifice. J. Justin Brown and Son were awarded the general contracting job and ground was broken on July 4, 1954.​

​On Laetare Sunday, March 11, 1956, Rt. Father Msgr. Cyril J. Vogel, Chancellor of the Diocese of Greensburg, representing Bishop Lamb, laid the cornerstone of the "new" St. Sebastian Church. The ceremony was attended by over 1,000 priests, nuns, parishioners, guests, and non-parishioners. Father Harkins served as deacon at the services and Father Charles Ribick, pastor of St. Edward in Fayette City, served as sub-deacon. Monsignor Vogel sealed into a cornerstone on the gospel side of the altar a copper receptacle containing a history of the church, names of the members and church groups, medals, papers, and other souvenirs.

Our joy, however, was short-lived when Father Martin died on April 10, 1956 following a siege of pneumonia. Although he did not live to see his plans become reality, he was there in spirit as Bishop Lamb permitted his funeral Mass to be the first offered in the new church.

St. Sebastian was without a pastor for two months following Father Martin's death. Father Henry Murphy, appointed a second assistant here on September 24, 1954, was named acting pastor by the Bishop and handled the pressing spiritual and temporal needs of the parish aided by Father Thomas McDonald, first resident assistant. Father Henry F. Hanse of St. Mary Church in Freeport was named the sixth pastor of our church and arrived on July 5, 1956. Father David Fisher arrived with Father Hanse as a new assistant replacing Father McDonald who was named pastor of St. Mary Church in Parker. Father Murphy was retained at the church by Bishop Lamb.

The parishioners were immediately informed by Father Hanse that he intended to carry out the plans for the new church and school which Father Martin had envisioned prior to his death. Sunday Mass was said for the first time in the new church on July 15, 1956. Sunday Masses were continued in the new edifice while weekday Masses were offered in the old church, as were the other services except on Holy Days of Obligation when Masses were also said at the new church. The new church was solemnly dedicated by Bishop Lamb on December 9, 1956. In subsequent years, the original pipe organ was dedicated, and a carillon, air conditioning, and stained glass windows were installed. The school opened for the first time on September 11, 1957 with 67 students, and in 1960, a house was purchased on Broad Avenue to serve as the Convent.

The parish continues to grow, now numbering over 1650 households and families. Currently over 250 students from Saint Sebastian and neighboring parishes are enrolled in the school. The former rectory now serves as the Parish Center, providing office space for the staff and meeting rooms for various parish organizations and groups.

The ministries, activities, and programs have increased over the years to meet the needs of the parishioners and the members of the local community.  In 2001, a Capital Campaign raised over $1,000,000 for renovation of existing parish facilities to ensure that the people, who are Saint Sebastian Church, may continue the ministry and mission of Jesus Christ today and into the future.