In October 2024, a broiler farm located south of Nouakchott, Mauritania, reported respiratory symptoms, diarrhoea, and 10% mortality within a flock of 4500 birds. Pooled organ samples (n?=?6) were collected and screened by real-time RT-PCR for H5 and H9 subtype avian influenza viruses, Newcastle disease virus, infectious bronchitis virus, and infectious laryngotracheitis virus. Six samples were positive for H9. Full genome sequencing of a representative sample revealed that the viruses were H9N2 and belonged to lineage G5.5. Several molecular markers associated with adaptation to mammalian hosts were identified indicating the virus’ potential to infect humans. Analysis of the eight segments showed that the virus was not a reassortant and that it was similar to H9N2 viruses identified in Senegal. This is the first report of H9N2 in Mauritania, and the data generated will be of interest to national and regional veterinary and public health authorities.