A chapel dedicated to St Mark, said to have had a holy spring nearby, is believed to have stood on the site before the present church was built. Tradition links it loosely to Mosjö in Närke, though this connection is very uncertain. The present building retains partly medieval stonework in its nave, with a narrower west tower topped by a four-sided timber lantern, a chancel to the east of similar height and width, and a porch to the north. Sources differ on some details of the building's development: one account describes a three-sided chancel added in 1730 and a nineteenth-century Neoclassical tower replacing an earlier bell-stage, with renovations in 1912 and 1941–42 uncovering earlier decorative schemes.
The most striking woodwork inside is largely eighteenth-century: the pulpit, altar fittings, altar rail, gallery and probably the altar and ceilings all date from that period, paid for in part by the Sparre family, who also funded the dark oil altarpiece of Christ on the cross, attributed to Johan Aureller the younger. The Sparres additionally gave a silk chasuble, a gilded wooden chandelier, pewter candlesticks and a brass christening bowl. A 1730 rebuilding is linked to Baron Carl Carlsson Sparre and his wife Märta Bonde; a burial vault beneath the chancel holds the remains of a cavalry officer named Fagerberg and three others.//
Among the older survivals is a damaged medieval wooden sculpture of the Archangel Michael on the south wall, missing its sword arm, and a set of carved lily-motif stones in the porch thought to date from the twelfth century. The unusual font, probably gilded plaster from around 1800 and possibly a spoil of war from Poland, takes the form of an eagle with outspread wings perched on a branch on the floor.
A seated wooden Madonna sculpture from the twelfth century, attributed to a west Swedish carver influenced by French style and compared to the so-called Viklau Madonna from Gotland, was removed to the Museum of National Antiquities in Stockholm; only a photograph remains in the chancel today. The church's medieval bells suffered a similar fate: the current bells date from 1916, cast by the Bergholtz foundry in Stockholm, which took the older bells in part-exchange. The smaller of the old bells, thought to date from the 1200s, was later acquired by the same national museum, though one source describes it instead as bearing a sixteenth-century Latin inscription naming a founder called Magnus — the two accounts do not agree on its age or origin.
Until 1962 Mo formed part of the Hjälstad parish grouping together with Vads and Sveneby churches, with Hjälstad as the mother church. Mo kyrka now belongs to Fägre parish and, since 2010, to Töreboda pastorate.