St. Trinity in Koszęcin is built of wood, oriented, carcass construction, on a stone and brick foundation.
A three-sided chancel, a sacristy with a beam ceiling, above it a collector's box open to the presbytery with stairs outside. A wider nave on the plan of an elongated rectangle, a small square porch next to it from the north. Music choir supported by four decorative poles and an organ from 1886.
Two towers: higher from the west - pole-shaped, with slightly sloping walls.
The main baroque altar from the first half of the 18th century, with gates, next to which there are paintings with allegorical scenes.