Holy Trinity was established on December 7, 1944. The origin of the parish can be traced back to 1906, when a group of residents in Moon Run formally petitioned the bishop for a new parish. The bishop determined that there were not enough Catholics in the area to support a parish. However, in 1908, a mission of St. Columbkille Parish, Imperial was established in Moon Run. Work began on a church and the first Mass in the parish was celebrated in the basement of the church on August 19, 1908. Work continued on the superstructure of the church and the completed building was dedicated on May 30, 1919.
Over the next 36 years, the population of Robinson Township grew slowly. By 1944, the diocese decided that the population had grown enough to support an independent parish. The parish was established and a resident pastor was assigned.
After World War II, construction of the Parkway West and the Greater Pittsburgh International Airport led to a rapid rise of population. By 1951, the parish began to outgrow its church. The parish purchased land for a larger parish plant in April of 1951. Construction of a school building that would include a temporary church began in 1952. The completed church/school building was dedicated on June 20, 1954. The old church was converted to a parish hall but was then sold in 1959
On August 9, 1964, ground was broken for the permanent church. On August 27, 1966, the first Mass was celebrated in the new church. However, the building was not formally dedicated until May 14, 1967.
With the turn of the century, trends in the Diocese of Pittsburgh began to reveal a decline in Mass attendance and sacramental participation. At the same time, the number of priests available for parish ministry also began to decline.
To address these challenges, Bishop David Zubik announced on April 12, 2015 a new diocesan initiative, On Mission for The Church Alive!, a consultative strategic planning process designed to foster viable, sustainable and vibrant parishes. As part of this process, the Bishop, in consultation with the faithful, began to consider new models of parish life based on pastoral needs, financial and temporal resources and available clergy.
In 2018, following the period of consultation, parishes were grouped together and served by a single clergy team to eventually form one new parish.
During this transition period, Holy Trinity Parish remained an independent parish while sharing clergy and staff and eventually publishing a joint bulletin with the other parishes. This ended on January 6, 2020 when Holy Trinity Parish merged with St. Malachy Parish, Kennedy Township and St. John of God Parish, McKees Rocks to form the new Archangel Gabriel Parish. As part of the merger Holy Trinity Church remained open as part of the new parish.