The adoption of Christianity as the official religion in the 4th C. A.D. by the Emperor Constantine meant the end of religious suppression and that churches started to be built. From the 5th C. many churches were built that were dedicated to St. Paul. Several of these churches, according to the European travellers that came here, were built in Tarsus, the birthplace of St. Paul. Nowadays only one survives and this is the reason that the Church of St. Paul is held in such high importance. The building covers an area of 460 m2 with the main monumental entrance to the north. Directly to the right of the entrance is a garden where the water well of the church is located.
The generally rectangular building has a relatively simple layout; on the west there is sloping vaulted roof supported by four columns, with the inside of the vaults painted sky- blue and decorated in the comers with stylised nature motifs. The main entrance is arched with a window on either side. The capitals of the columns are in Corinthian style. The floor of the church is made up of black and white marble tiles with a small area in front of the praying area behind done with a simple arrangement of triangular black and white marble. At the intersection of the central nave and the apse there is a decorated marble screen separating the hoc area. The niches of the interior walls are decorated with religious icons and representations of saints. There are similar niches in the smaller side apses. To the east of the central nave, next to the window above the central apse, there are depicted two angels amongst clouds. Below the window there is a landscape painting. Above the angel motifs there is an eye motif in a triangle on the central vault. In the next scene the Evangelists (the writers of the Bible) are represented alongside Jesus in the centre. The figures are represented as wearing clothes of red and blue. The right hand of Jesus is extended outwards and the apostles are writing the Bible.
To the side, front and left, are depicted Luke and a bull with Matthew behind him. The upper section of this figure, from the shoulders, has been destroyed; only the name can be made out in one place. Right and forward are depicted Mark and a lion with John and an eagle behind him. There are two more small doors on the north and south sides of the church. On the side of the door to the south there is an external double staircase which gives access to the gallery of the church. In the gallery (overlooking the central nave), made of wood in the shape of a balcony, there are landscape paintings on the balustrade.
There are symmetrical windows in die apses and sides which provide light for the interior. The windows above the small doors on the sides are in the shape of a cross. To the right side of the northeast of the building there is a bell tower supported by a small column.
The current condition of the church is the result of major renovation and architectural works undertaken in 1862. The church was abandoned when the Christian population of Tarsus left in 1923 and it was later partly converted and used for various purposes. In 1994 it was adopted as a protected building by the Ministiy of Culture and Tourism and was designated as a monument museum. It went under a major restoration for protecting its architectural characteristics and frescoes.