Earliest of the Roman Catholic parishes in Walnut Park is that of the Nativity of Our Lord, which was founded late in 1904, as the result of petitioning by the Catholic residents. Its first services were held in the chapel of St. Mary's Orphans Home in December, 1904. A combination church and school was dedicated on October 22, 1905, at 5513 Oriole Avenue. The church was extensively remodeled in 1955. Portable classrooms were built near the church in 1921, and the present school building at 5827 Harney Avenue was opened in 1922 with a new addition in 1948. In 1931, the convent was erected. The original large Nativity parish was later broken up to create the new parishes of St. Adalbert, St. Philip Neri and the Corpus Christi parish in Jennings. A Polish Catholic church was established in 1913 and named for St. Adalbert, the patron saint of Poland. At first the congregation worshipped in the chapel of St. Mary's Orphanage. Its first church was dedicated in 1915 at 5710 Woodland Avenue, while the present church was completed in 1956. Polish services were only recently discontinued. St. Adalbert parish opened its parochial school at 5701 Amelia Avenue in 1927, and a new addition was placed in use about 1960.
The church of St. Philip Neri was organized on June 26, 1919 by Rev. Thomas Kennedy. Cornerstone laying ceremonies for a combination church and school occurred on November 7, 1920. The structure was completed in September 1921, at which time the parochial school was opened. The parochial school at 5036 Thekla Avenue was later used as a branch of the Mark Twain School. The church is now located at 5046 Thekla Avenue and the convent is at 5079 Queens Avenue.
The first religious denomination to organize in Walnut Park was a Lutheran congregation in August 1901. It met in the homes of members until a church was completed at Harney and Gilmore. This building was used until 1950, when the church, named for St. Matthew, moved to a new structure at 5402 Wren Avenue. Its first elementary school was opened in 1950 at 5403 Wren, across from the church.
Difficulties in reaching church on Sunday led several German women in the Walnut Park area, then known as "the Stix" to begin a movement to organize a German Evangelical church there in 1906. A house-to-house canvass brought together an interested group and in May, 1906, the Ladies' Aid Society was organized. It soon developed into a congregation and first services were held in a barn, belonging to Edward Heuer on Wren Avenue. Shortly thereafter, a small frame church was built at Plover and Thekla Avenue. Growth of the congregation was slow in the first decade because all services were conducted in German. English was introduced in 1917, broadening the church's field. Despite an enlargement, the original church became inadequate by the 1920's. Named as Salvator Evangelical, a combination church and Sunday school was built adjacent to the old church in 1925. The present church, now known as the Salvator United Church of Christ, was built on the site of the original one at 5618-22 Thekla, in 1951. At that time, the older adjoining building was remodeled into a meeting hall and offices.
A German Presbyterian church was founded in 1901 at 5451 Robin Avenue, but was disbanded during the depression of the 1930's. Two Baptist churches have been in the area for many years, these are the Walnut Park Baptist; church, at 4952 Emerson and the West Florissant Baptist church, at Florissant and Mimika, to which an addition was built in 1955. Other churches in the Walnut Park area are the Mount Beulah M.B. Church at 5209 Lilian, the Rose Hill M.B. congregation at 6102 Emma and the Bethel Temple Church of Christ at 5075 Davison Avenue.