St. Valentine was established as a mission church of St. Anne, Castle Shannon in 1923. Before the parish was founded, local Catholics had to travel to Castle Shannon to attend Mass. In the summer of 1922, the pastor of St. Anne organized a catechism class, which was held in the Coal and Iron Police barracks. On September 9, 1923, he celebrated the first Mass in Bethel Park, then called Coverdale, in a rented storeroom. In 1925, land was purchased for a church building. In March of 1926, the St. Anne pastor purchased the original St. Bernard Church. The building was taken apart and moved to Bethel Park. Half of the material was used to build a church and the other half to build a parish hall next to the church. The new church was dedicated in the spring of 1926.
On September 10, 1931, St. Valentine was formally established as an independent parish. The church was remodeled and enlarged with the addition of a sanctuary around 1940. On July 19, 1942, a fire broke out in the church during the benediction following Sunday Mass. In the ensuing panic, 35 people were injured, though none seriously. The fire destroyed the church and inflicted enough damage on the adjacent parish hall that it had to be torn down. While the parish worked on building a new church, Sunday Mass was celebrated in the Bethel Park Fire Hall.
The cornerstone of the new church was laid on October 18, 1942, and the first Mass in the new church was celebrated on Easter Sunday, April 25, 1943. The church was formally dedicated on May 31, 1943. Following World War II, the suburb community of Bethel Park began to rapidly grow. The congregation soon outgrew the existing church. At one point, the church set up a portable altar in the basement of the school and held Masses simultaneously in the church and school.
On July 25, 1965, ground was broken for a new church. The old church was torn down, except for a portion of the building that was preserved as an Administration Building. During the construction of the new church, Mass was celebrated in the school basement. The cornerstone was blessed on November 10, 1966, and the first Mass in the new church was celebrated on Christmas Day, 1966. The church was formally dedicated on November 23, 1967.