The church's growth reflected the fortunes of the city and during the last quarter of the 19th century, when Tullahoma was promoted as a growing business center and a health spa for those from the lowlands seeking the benefits of cool nights and spring waters, the church grew as well. It became a center for mission work, particularly under the leadership of Dr. Henry R. Howard (1882-1895). In 1897, a cornerstone was laid for a new, larger building - a Gothic Revival-design of Chattanooga architect H.L. Hunt. The walls were constructed of Sewanee sandstone and the roof of slate. This structure is still in use today.

After Howard's death, St. Barnabas lost its prominence as a missionary congregation; the clergy, who came and went, regarded their primary purpose as holding services. Membership dropped from 67 listed in 1898 to 32 in 1902, perhaps in part because Tullahoma's health resort business was declining with visitors preferring the higher elevations of Monteagle.

The Tennessee Vocational School for Girls was established nearby in 1915 and during the years 1920-1944, St. Barnabas provided worship opportunities for the girls and a number were baptized and confirmed. A big event for Tullahoma and St. Barnabas was the coming of World War II and the establishment nearby of Camp Forrest, a major army training camp. St. Barnabas responded, with diocesan help, by building a social center for the soldiers. This 1941 building with renovations and additions has served as the parish house since the war. Church attendance rose during the war and declined afterward until Arnold Engineering Development Center was established in 1952 on the old Camp Forrest grounds sparking a new growth period. St. Barnabas aided in the establishment of St. Bede's Church in Manchester in 1962.

A Sunday School wing was added in 1974 and a new Parish Hall was built in 2002 The church is noted for its beautiful stained glass windows whose symbolism serves as an inspiration to all who worship there.