Kajar was first mentioned in a charter from 1037, when King St Stephen bestowed the village on the Bakonybél Abbey. The church was built in Baroque style between 1797 and 1880, boasting a single nave, mitred vaulting and an organ gallery as well as a flat-ceilinged sanctuary. The tower rising from the flatness of the facade (similar to the Benedictine churches of neighbouring villages) has a so-called “hen-roost-roof” design and a shingle roof. The Empire-style unusually coloured high altar and pulpit as well as the neo-Classical and late-Baroque-style pews are probably the same age as the church. The high altar picture depicting the Holy Trinity was painted by József Schmidt in 1799. The fresco on the sanctuary ceiling depicts the Lamb of God, the four evangelists and the Benedictine monastery at Bakonybél.
The Turkish destroyed the Evangelical oratory in the church in 1683. Then a wattle church was built, which burnt down in 1727. The church raised in its place was consecrated in 1730. A new, larger stone church was built in Baroque style in 1788, following the Tolerance Edict. The church’s interior was completed in 1794. The two-sided gallery, with stone legs and a coffered front wall, and the ceiling are both made of wood. The old pulpit was demolished in 1913 and replaced with a new one. The church organ was also made at that time. The church has been renovated several times over the last sixty years and the conversion of the organ to a mechanical one has been completed. The names of those who died in the two world wars can be found on the memorial plaques on the wall. There is also a memorial plaque in honour of the preacher, János Szentmiklós, who was held captive for his faith between 1774 and 1776. In 2017, on the 500th anniversary of the beginning of the Reformation, a plaque immortalising the names of all the ministers serving the congregation since 1609 was added to the wall of the parvis.