The original church is thought to have been built in the 12th century as a centrally planned building with transept arms. In the early 14th century it was substantially rebuilt, giving it much of its present appearance: a two-aisled nave with a narrower, straight-ended chancel. The tower at the west end stands noticeably out of true, apparently because the builders originally intended to construct a three-aisled basilica; the southern aisle was never completed, leaving the tower askew and the church with its unusual two-aisled form. A sacristy was added on the north side in 1729.
Inside, the vaulting reflects this two-stage construction, with older surviving vaults from the medieval church contrasting with later additions. The north wall carries surviving sections of a wall-painting frieze attributed to the so-called Passion Master, painted in the 15th century, depicting scenes running from the institution of the Eucharist through to the Pentecost miracle. Further painted decoration in the vaults dates from the 18th century.
Among the church's furnishings is a sandstone altarpiece made in 1792, which originally featured a lamb bearing a cross-banner at its centre; in 1955 this was replaced by a Calvary group said to date from 1280. A triumphal crucifix is attributed to the mid-14th century, and a font from the late 13th century has been associated with the workshop or style known as Semi-Byzantine. The pulpit, with its sounding board, is executed in a Renaissance style, and fragments survive of a 15th-century altar cabinet depicting the Coronation of the Virgin. The pews throughout are 18th century in date.
The organ was built in 1887 by M. J. Lindegren of Gothenburg, with later work altering its disposition in 1953 and again in 2002; it remains a mechanical instrument.
Across the road to the east of the church stands the remains of a kastal, a defensive tower of a type found at several Gotland churches, of which the example at Gammelgarn is considered among the best preserved. At Hamra only a low, rounded mound survives, around two metres in diameter and just over two metres high, now overgrown with deciduous trees; it is said locally to have also served at some point as a lime kiln.