Recurrent long- and short-term Neanderthal occupations occurred in the Abric Romaní rock shelter (Capellades, Barcelona, Spain) for more than 20,000 years. This provides an opportunity to enhance our understanding of the evolution of behavioral strategies of these human groups. The site has a long and high-resolution sequence with 17 levels completely excavated, 13 of which are presented in this work, from D to Q; ca. 40–60 ka. These levels have generated extensive research concerning Neanderthal hunting strategies, lithic production, and fire technology. Here is presented the evolution of palaeoenvironment under which these populations lived applying different methods of palaeoecological reconstruction based on small-mammal remains along the entire sequence. The study is completed with taphonomic analyses that locate the primary origin of their accumulation under the action of owls and describe a past humid fossiliferous microenvironment where intense human occupation occurred. Oxygen isotope analyses were performed on rodent incisors from the richest levels (D, E, N and O), in order to reconstruct the past air temperatures. The medium to low intra-level ranges of oxygen isotopic values indicate a period of preferential accumulation moment of small mammals, which is likely related to spring-summer predator activity. Throughout the sequence, the landscape evolution is marked by an extended forestall cover and abundant water resources, both integrated in a patchy landscape. Climatic conditions were globally cooler and slightly wetter than present, but rather stable across the sequence. The greater relative presence of mid-European small-mammal species and the estimated lower palaeotemperatures correspond to relatively cooler episodes, such as stadial events, in levels E and O. However, certain discrepancies in palaeotemperature estimations are detected between oxygen isotopic analyses and other methods based on species occurrence. Northeastern Iberia environmental conditions related to Mediterranean climate provide a favorable MIS 3 scenario compared to European higher latitudes. Indeed, the milder glacial fluctuations detected within the Abric Romaní site are coeval to other Iberian Middle Palaeolithic sites with long-term occupations and allow these human groups to incorporate this region for millennia in their migration routes.