It is a three-aisled cruciform church with a west tower. The tower, choir and transept were built around 1500 in late Gothic style. The nave and aisles were rebuilt and enlarged around 1763 by Barthélemy Digneffe on behalf of Augustina van Hamme, abbess of Herkenrode. The side aisles and the central aisle were then placed under one roof. Restoration work took place from 1872-1874 and the tower was restored in 1901. A portico was added in 1929. In 1965 a sacristy with chapel was added. The square tower is built in iron sandstone. It has three sections, separated by marlstone drip moldings. The tower has a polygonal stair turret on the south side. The actual church building is built in brick, on a plinth of iron sandstone, and with the use of limestone and marlstone for corner bands and the like. The choir has a three-sided closure, and the pointed arch windows were bricked up in 1763. A coat of arms with the motto of the abbess, Regique deoque (for king and God) is above an earlier, now bricked up door. The interior of the church is classicist. The baptistery used to be a chapel founded by Prince-Bishop Everhard van der Marck. Most of the furniture (communion rail, main and side altars, confessionals) are from the third quarter of the 18th century and the pulpit is from . A late Gothic, oak crucifix from the early 16th century hangs against the west facade of the southern aisle, and a painting depicting Saint Gertrude of Helfta hangs above the main altar. There is also a Gothic triumphal cross from the second half of the 15th century in the transept. In the presbytery there are a number of statues that vary in age between the 13th and the 17th century, such as Gertrudis van Nijvel (first half of the 13th century), Our Lady and Child (around 1400), Christ on the Cold Stone (15th century), Saint Bernard and Saint Gertrudis (16th century) and John the Baptist (early 17th century). A painting depicting the Mystical Marriage of Saint Catherine is from the late 17th century. A relief on a buttress of the choir shows how Prince-Bishop George of Austria gives his heart to Gertrudis van Nijvel. This heart is in a late 16th century epitaph in the church.