A bryozoan fauna containing 11 species is described from the Lower Devonian (middle Lochkovian) of Arroyo del Agua, Sierra de Guadarrama, Guadalajara, Spain. One genus containing one species is new: rhabdomesine cryptostome Fehlerpora insolita n. gen. n. sp. Six additional new species are described: three cystoporates: Cystiramus gracilis n. sp., Fistuliramus guadarramaensis n. sp., and Fistuliphragma tenuis n. sp.; and three trepostomes: Eridotrypella hispanica n. sp., Boardmanella dubia n. sp., and Leptotrypella inesae n. sp. Four further trepostome species were identified: Leioclema incompositum Duncan, 1939, Minussina spinosoformis Astrova, 1964b, Leptotrypella verisimilis Astrova, 1970, and Leptotrypella vulgata Astrova, 1964b. The association is distributed over three different sedimentary environments. The high-energy one representing accumulation of debris from bryozoan-coral-pelmatozoan thickets contains eight species dominated by erect branched forms (six species). Tabulate corals are present, especially branches which most likely belong to Subcladopora? abnormis (Mironova, 1974). The environment with moderate to low wave influence contains only two bryozoan species, one erect branched and one encrusting. The third setting represents bryozoan thickets in situ situated in deeper water, the most tranquil environment characterized by four bryozoan species, dominated by three erect forms. Fenestrate bryozoans are absent from the two higher energy environments, whereas the bryozoan thickets in deeper water contain rare unidentified fragments of fenestrates. The bryozoan fauna shows distinct relations to the Lower Devonian (Lochkovian) of Ukraine, one species is known from the Middle Devonian of U.S.A.