The earliest mention of a Catholic presence in the Ivy Mills area is 1729.  Mention of Mass being celebrated in the home of the Willcox family was made in the diary of an English Jesuit priest from the colony of Maryland.  They met in the home of Thomas Willcox, who had a house and paper mill at present-day Ivy Mills and Polecat Roads. The tiny congregation gathering on the Willcox property was the beginning of what would eventually become the parish of St. Thomas the Apostle.
Jesuits continued to minister to the Ivy Mills congregation until 1790, when priests from Delaware took over the spiritual needs of the Catholic community at the Mission at Concordville (Ivy Mills) Prominent among them was Father Patrick Kenny, who arrived in Wilmington in 1804 and ministered to souls in Delaware and SE Pennsylvania until 1840, when priests were then sent out to Ivy Mills from Philadelphia.
Mass was celebrated on the Willcox property until a church was constructed, in 1852, on land donated by James Mark Willcox, the grandson of Thomas. The cornerstone was blessed by St. John Neumann, fourth Bishop of Philadelphia, on September 2, 1852. Built of fieldstone and covered in blocked stucco, the church has been in continual use ever since.  With the appointment of the first pastor, the parish of St. Thomas the Apostle was officially established and ceased to be a mission.
The first resident pastor, Fr. Charles Maugin, arrived in 1856. As the Catholic population of the area grew, St. Thomas established the missions which developed into the parishes of Nativity BVM in Media and St. Cornelius in Chadds Ford. 
The church was renovated in 1897, when stained glass windows and a vestibule were added, and again in 1937, when electric lighting was installed and the exterior stucco removed, exposing the native stone. In 1956, a parish school was built, along with a small convent for the teaching nuns. These improvements helped complete the ministry of the parish to a congregation now growing very rapidly, and Saint Thomas celebrated its 250^th Anniversary in 1979.
The parish met the challenges of continued expansion by building a new church and rectory in 1990-1991 on land adjacent to the 1852 church. The convent was razed, and in September 2000, classes were held on the first floor of the new Parish Educational Center. A second floor and a brand new gym were added in 2001. Saint Thomas serves as a regional school and was named a National Blue Ribbon School by the U.S. Department of Education in 2017.
In July, 2020, the parish was entrusted to the Oblates of St. Francis de Sales, with Rev. Stephen Shott, OSFS, as pastor. The parish continues its tradition of vital growth and witness.