In early 20th century, significant numbers of Romanian immigrants began settling in Northern Liberties alongside other Eastern European groups. Most of them came from Transylvania and Banat, two Romanian provinces then under Austro-Hungarian occupation. Settled around St. John’s Church, they formed a true Romanian "neighborhood".

The first evidence of their presence in Philadelphia dates back to 1906 when the "Bãnãţiana" Society was established. Its headquarters was located on Brown Street, across from St. John’s. Thus, the church was to become a beacon and a providential place to these pioneer Romanian immigrants.

Because they did not have a church of their own, The Society’s main hall served temporary place for their Sunday gatherings, when they prayed and sang their home church hymns (“pricesne”), thus relieving their longing for beloved ones they had left behind. From time to time, when occasionally a visiting priest arrived, they came to attend the Divine Liturgy, to listen the Gospel, to confess and receive the Holy Communion.

In such a Sunday in 1913, after the celebration of Mass performed by father Moise Balea, a group of Romanians decided to establish a Romanian Orthodox parish, or - as a document from 1931 puts it - a parish according to our "ancestral law (faith)". And since that Sunday, June 13th, was the Feast of Pentecost, they thought it was only appropriate to name their parish „Descent of the Holy Spirit”, and thus to place their community under the sign and protection of the Holy Spirit. They continued to hold the religious services in the society’s social hall, until 1919, when they were given the chance of using -free of charge - the first floor of St. John's parish school across the street. Later, they arranged to share St. John's sanctuary with the Episcopalians. The two congregations continued to share the church until 1923, when the Episcopal Diocese gave them exclusive use of all the Church buildings and property for an unlimited period of time, for an annual fee of $15.

In 1929, the first permanent priest arrived, in the person of Father John Popovici (1890-1973), who served the community for nearly 40 years. During his tenure, in 1931, the church was consecrated, and, in 1937, the parish came under the authority of the Romanian Orthodox Missionary Episcopate, whose first primate was Bishop Polycarp Moruşca (1935-1958).

Unfortunately, in the '60s, Northern Liberties neighborhood has experienced a period of decline and much of Romanian moved to the northeast of Philadelphia. Accordingly, part of the community has left the church in Brown Street, and in 1965 the parish was relocated to Elkins Park, a suburb of Philadelphia. Community has thus divided it into two.

A difficult period followed after the spilt for those who have remained faithful to the church on Brown Street. However, despite the difficulties of all sorts, in 1972 Holy Trinity managed to become the owner and to take full possession of the church building and properties. The Romanians took the property in 1972.The church windows have subsequently been restored during the tenure of the late Fr. Octavian Băluşel. In 1983, in recognition of its historical and architectural values, the church was included in the National Register of Historic Places.

After some years of declining membership, Holy Trinity's congregation was reinvigorated by an infusion of young congregants in the late 1990s. Since 1999, a series of renovations and modernizations have been made: under the leadership of Fr. Florin Constantin Şalgău, the church roof was redone and the church steeple (bells tower) was remodeled. Also, a folk-style-carved wooden cross was brought from Romania and has been placed in the front of the church, paying homage to the heroes who died in the Romanian Revolution of 1989.