The church of Santa María de Vilamòs has a three-nave basilical ground plan. The central nave and the south side are barrel-vaulted, the north lateral vault is a quarter sphere and the whole structure rests on circular pillars finished off by a smooth impost. The most recent restoration work carried out uncovered the configuration of the internal masonry of the building, with an ordered layout of the ashlars, a very Romanesque trait.

The belfry of the church is attached to the centre of the south wall; this is, together with that of the church of Bossòst, the only Romanesque belfry conserved in the Aran Valley. The layout of the openings and decorative elements of the belfry of Vilamòs are totally Romanesque in style, as endorsed by the semicircular arched windows and the decorative columns which run along the body of the tower.

The absidal head was added in the Gothic period and the original Romanesque apse was replaced with a polygonal one. The access door to the temple, originally located in the south wall, is now in the west wall and dates from relatively modern times (1816).

Some of the most interesting artistic attractions of the church of Santa María of Vilamòs are the Roman gravestones embedded into different parts of the walls, although those located in the belfry tower, which can be seen from the outside, are particularly noteworthy.