Marine algae and foraminifers occur in the Ancient Wall carbonate complex of Upper Devonian (Frasnian) age in Jasper National Park, Alberta, Canada. This microbiota is the most diverse and abundant yet described and illustrated from North America; it closely resembles other microbiotas from the Upper Devonian of Western Australia and the Volga–Urals region of the Soviet Union.Strata of the Ancient Wall complex comprise two formations each with two members. They are: the Cairn Formation with a lower Flume Member and an upper member and the overlying Southesk Formation with a lower member and an upper Simla Member. A biota of 15 genera and 21 species is recorded from these rocks. The forms grouped under the algae are: Vermiporella sp., Girvanella sp., Sphaerocodium sp., Renalcis sp. cf. R. turbitus Wray, R. sp., radiosphaerid calcispheres, and algal? borings. The calcareous foraminifers are: Parathurammina sp. cf. P. spinosa Lipina, P. sp., Bisphaera sp., lagenid-like form, Paratikhinella sp. cf. P. cannula (Bykova), P. sp., Tikhinella sp. cf. T. measpis Bykova, T. sp., Evlania? sp., Eonodosaria sp. cf. E. evlanensis Bykova, E. sp., Multiseptida sp. cf. M. corallina Bykova, M. sp., and Nanicella sp.Calcareous foraminifers, dominantly parathuramminids, comprise about two-thirds of the total biota. The remaining one-third consists of algae, amongst which radiosphaerid calcispheres are the most abundant. The relatively primitive parathuramminids are more numerous in the Cairn Formation, whereas more advanced foraminifers such as tikhinellids, eonodosarids, and multiseptids occur more frequently in the overlying Southesk Formation. There is also an appreciable increase in foraminiferal diversity between the basal Flume Member and upper member of the Cairn Formation. Radiosphaerid calcispheres and parathuramminids are most numerous in skeletal wackestones and tikhinellids, eonodosarids, and multiseptids in less muddy packstones and grainstones.Study of this biota substantiates previous interpretations of the depositional environment based on stratigraphic and petrographic evidence. In general, these indicate shallow-water environments for both the Cairn and Southesk Formations, with the packstones and grainstones, which occur more frequently in the Southesk Formation, indicative of more agitated and presumably shallower waters.