The rescue excavation of the Balagny-sur-Thérain habitat site (Oise, France) was conducted in 2015. Located within the alluvial plain of the Thérain, two sectors were excavated, covering a total area of 441 m². Despite a compacted stratigraphic sequence, the layer of remains, composed of lithic pieces and some bone fragments, is remarkably well-preserved with little post-depositional disruption. Radiocarbon measurements, as well as the other analyses performed make it possible to assign the occupation to a specific lithic industry with a chronological attachment: the segment and projectile point industry, whose lithic reduction sequence includes the modification of their bases. This complex is known in northern France (“Beuronien à segments” or Beuronian with segments) and is dated between 9200 and 8700 BP uncalibrated, i.e., between 8500 and 7500 cal. BC. The excavation and study of these concentrations of material culture, which are spatially close to one another, is part of ongoing and current research on the paleoethnology and mobility of these Mesolithic groups. Balagny-sur-Thérain also documents the first part of the Beuronian with segments period, and reveals some emerging particularities relative to the projectile points. Finally, the discovery of one such fragment within a boar bone illustrates hunting activities in a concrete manner. This find is exceptional within the context of the Mesolithic period in France.