Micromammals form a group that includes four orders (Rodentia, Lagomorpha, Eulipotyphla, and Chiroptera), whose common feature is not only their small size but also their phylogeny. Its utility in palaeoecology is linked to the preference of each taxon for a specific type of habitat, sometimes even being restricted to one of them (López-García, 2008). Besides, they are highly sensitive to environmental changes . They are also useful in biostratigraphy because of their quick evolution and high reproduction rate (Herráez & Sesé, 1993). These features, together with the large number of remains preserved in palaeontological sites compared to macromammals, make it possible to conduct highly accurate studies about the chronology and climate of specific levels in Quaternary fossil sites. Results can be compared with other palaeoclimatic proxies, such as the ice-and marine cores, or even absolute dating in the specimens with higher relevance. This allows for a better understanding of the environment they lived in, as well as obtaining a more accurate time frame for the micromammal association. This paper provides a study of the remains of micromammals present in Level 0 of Cueva del Hueso, focusing on the following main aims: (1) to carry out an anatomical and taxonomical study of the micromammal fauna recovered at this deposit, (2) according to the data obtained from the taxonomical study, to perform a palaeoenvironmental study that sheds light both on the climate and landscape in the surroundings of the cave, when it was inhabited by the identified species, (3) to conduct a study on the palaeobiogeography of each species separately, as well as the association as a whole, to estimate a chronological frame from the association of micromammals so that the environmental interpretation made can be set.