Urban rivers are very important elements of the urban landscape, but increasingly degraded by human activities. We studied the composition and emergence patterns of odonates in three sectors of an urban river, the Sarela, in Santiago de Compostela, north-western Spain, to evaluate its ecological state. Exuviae collection was carried out weekly between May and September 2022. We found exuviae belonging to six species, the most abundant being Boyeria irene, Cordulegaster boltonii and Onychogomphus uncatus, and we report the occurrence of Oxygastra curtisii in this river for the first time. This community is typical of medium sized rivers in the region. We analysed whether the emergence (both in relation to date and abundance) varied depending on the species, sex and the section of the river, based on the three most abundant species. The sex ratio was similar in all species, and the section of the river did not affect the mean date of emergence, but density was clearly different among sections. There were significant differences among species in emergence patterns, with O. uncatus emerging earlier, then C. boltonii and finally B. irene.