The National Museum of Iceland located in Reykjavik houses a rich collection of embroidered church and secular textiles from the late Middle Ages to early modern times. The collection contains objects of cultural and historical significance including altar cloths and valances or wall hangings. The majority are needlework on lérept or literally ‘linen’, a general term referring to tabby woven fabrics made of plant fibers. The collection is unique, not only beause of the age of the textiles and their abundant colorful embroidery with figurative and narrative elements, but also that they are embroidered and not patterned by weaving techniques,which was more common in similar textiles made by local women from other regions of contemporary Scandinavia. Previous research suggests that Icelandic church textiles were made of imported flax fabric rather than being grown and woven locally, also that a lot of the needlework was carried out by local women. In this research selected accessions were analytically investigated with microscope techniques using the “three-stage procedure” to identify the botanical origin of the plant fibers yarns. Our investigation shows that the foundation fabrics were made of either flax or hemp, and that we cannot rule out local production of plantfiber yarns and fabrics.