For the first 91 years of its existence, St. Thomas's was located in a Gothic Revival church at Orange and Elm Streets in downtown New Haven. In 1931, the church built a new parish hall on Whitney Avenue in the East Rock neighborhood. Eight years later, a new church building was completed adjacent to the parish hall. The church building was made possible by a gift from a parishioner, C. Purdy Lindsley, M.D., as well as the Rectory and part of the endowment we enjoy.

The buildings were designed by the Boston architecture firm of Allen, Collens & Willis, who also designed Riverside Church and The Cloisters in New York. Its architecture is in the English Gothic tradition, with stone masonry walls and slate roofs. Our worship space has a cruciform plan with a tower over the crossing. Within the nave are stained glass windows depicting scenes from the life of Christ. Above the gallery at the rear of the church is a rose window given in memory of Caroline Ackerman Lindsley by her husband, Dr. Lindsley. Adjacent to the main worship space is the Lady Chapel, an intimate setting that we use for our 8:00am Sunday Eucharist and other small services.

In 1992, the church added a new wing to the south and west of the parish hall to accommodate the growth of St. Thomas's Day School. Designed by the Office of Michael Rosenfeld, the one-story addition includes classrooms and office space for the school. At the same time, an elevator was added to the parish house and the church landscaping and playground were improved. The project won a national award for design excellence from the American Institute of Architects.

Just south of the church on the Whitney Avenue side is a columbarium garden established in 1995 through gifts from Mr. Jack Bumstead in memory of his mother, Catherine Bumstead Turnbull. Within the garden, three granite monuments bear the names of those whose ashes are interred there.

Along the strip of land between the School addition and Ogden Street, the School has built a Garden to be used and maintained by students.

In New Haven: A Guide to Architecture and Urban Design (1976), architectural historian Elizabeth Mills Brown wrote that St. Thomas's is "the gracious keynote of this whole end of the Avenue," and likened the church in its relationship to adjacent Edgerton Park to "the parish church in the village at the foot of the great estate."