In this article, a zooarchaeological and isotopic analysis is presented for 26 dog exemplars (Canis familiaris). These dogs were deposited in burial and ceremonial structures in the northeastern Iberian Peninsula during the Middle Neolithic, within the Pit Grave cultural horizon (ca. 4200–3600 cal BC). Four archaeological sites of the Catalonian coastal strip are studied: Camí de Can Grau, La Serreta, Ca l'Arnella, and Bòbila Madurell (one of the most important necropolises of the Iberian Peninsula). The presence of these dogs is interpreted as evidence of accompanying offerings and represents the most ancient use of this animal in the context of burials within the studied territory. Although it is a not a globally recorded gesture during this period, in light of the present results, it can be considered as a stereotyped ritual activity and evidence of the close relationship between these animals and the human communities. The diet of most of the dogs must be considered mixed and very similar to that of the humans, including consumption of herbivores and terrestrial plants.