In Palaeolithic research, there has always been a need to understand the relationship between mobility, territoriality and the resource exploitation of hunter-gatherer groups. In the present study, we combine the data obtained from the archaeopetrological analysis of chert tools, which include textural, micropalaeontological and geochemical analyses, with geographic information to explore mobility in the Pyrenees region. We have applied computational techniques of spatial analysis, specifically Least-Cost Paths, to identify key natural routes and connectivity areas between chert outcrops and the archaeological site of Montlleó. The site, which is located in the middle of the Pyrenean valley of Cerdanya, has provided ample evidence that the region was already populated by past human groups during the Upper Palaeolithic. Archaeological works at Montlleó point to a long sequence of human occupations dated to between 23,000 cal BP and 17,000 cal BP during the Late Glacial Maximum. Studies focusing on the characterization of the lithic industry have revealed a polylithological toolkit, with chert being the rock in greatest use. The archaeopetrological analysis has shown the existence of a wide variety of exploited chert, which came from both sides of the Pyrenees mountain range. As a result, it has been possible to identify the natural routes of passage and infer the territoriality and social interactions of Palaeolithic hunter-gatherer groups who settled in the Pyrenees.