Thomas Welsh was born in Weatherly, Pennsylvania, one of five children of Edward C. and Mary A. Welsh. Raised in a strict Irish Catholic family, he received his early education at the parochial school St. Nicholas Church in Weatherly. He then attended Schwab High School, also in Weatherly, and later began his studies for the priesthood at St. Charles Borromeo Seminary in Overbrook in 1937.
Priesthood
On May 30, 1946, Welsh was ordained a priest by Cardinal Dennis Dougherty at the Cathedral of SS. Peter and Paul. He was then sent to continue his studies at the Catholic University of America in Washington, D.C., where he earned a doctorate in canon law in 1949. During his summers at the Catholic University, he served as a curate at St. Paul Church in Philadelphia, Maternity of the Blessed Virgin Mary Church in Philadelphia, and Our Lady of Mount Carmel Church in Doylestown. In 1949, Welsh became a professor at Southeast Catholic High School in Philadelphia. He was assigned as a curate at Holy Child Church in Philadelphia in 1951, and named a member of the Archdiocesan Metropolitan Marriage Tribunal in 1958. He was appointed vice-chancellor of the Archdiocese of Philadelphia in 1963. He was raised to the rank of Monsignor by Pope Paul VI in September 1965, and became rector of St. Charles Borromeo Seminary in 1966. During his tenure as rector, he oversaw an extensive revision of the curriculum, which earned the seminary accreditation with the Middle States Association of Colleges and Schools; the construction of a new theology wing named Vianney Hall; and the establishment the School of Religious Studies and the School of Pastoral Studies.
Welsh was appointed the first Bishop of the newly erected Diocese of Arlington in Virginia on June 4, 1974. He was installed on August 13 of that year. During his tenure, he established six new parishes and dedicated eleven new churches. He established the Office of Migration and Refugee Services in 1975 and the Family Life Bureau in 1977. Bishop Welsh also began the diocesan newspaper, The Arlington Catholic Herald. He was the founding president of the board of the Catholic Home Study Institute which became the Catholic Distance University. The number of Catholics in Arlington increased from 154,000 to 179,000 under his guidance.
Allentown
Following the resignation of Bishop Joseph M. McShea, Welsh was appointed the second Bishop of Allentown in his native Pennsylvania by Pope John Paul II on February 3, 1983. His installation took place at the Cathedral of St. Catharine of Siena on March 21 of that year. During his tenure, he established a "Stand Up For Life" campaign to encourage anti-abortion efforts, and frequently joined local abortion protesters for their monthly vigil at the Allentown Women's Clinic in Hanover Township. He held workshops on natural family planning and Humanae Vitae for the diocesan clergy. Welsh established the first Youth Ministry Office in the diocese and raised $13 million in an endowment campaign for diocesan schools and other educational efforts. He was a member of the Board of Trustees and Executive Committee of the National Shrine of the Immaculate Conception in Washington, D.C. Despite his reputation as a conservative, Welsh allowed girls to serve as altar servers at Mass, and gained recognition for his work to improve relations between Catholics and Jews. He turned his home, a mansion purchased by Bishop McShea and bequeathed to the diocese upon his death, into a center for carrying on his pastoral work. In 2018, Welsh was included in a report about cover-ups in six dioceses of Pennsylvania of child sexual abuse by priests. In the report, there are copies of correspondence with Bishop Leroy T. Matthiesen, referred to retired priest in Matthiesen's diocese as a recovering alcoholic. Bishop Welsh expressed concerns that the priest continue to be closely supervised. In 2002, the priest was arrested for abusing a 15-year old boy.
After reaching the mandatory retirement age of 75, Welsh resigned as Bishop of Allentown on December 15, 1997. He was succeeded by Bishop Edward Peter Cullen, who, like Welsh and McShea, served as an auxiliary bishop of the Archdiocese of Philadelphia before his appointment to Allentown. During his retirement, Welsh continued to administer the Sacrament of Confirmation at parishes around the diocese. Welsh later died at Lehigh Valley Hospital at age 87. He was buried in St. Nicholas Cemetery in his native Weatherly.
