The vomeronasal organ (VNO) or Jacobson’s organ is an auxiliary olfactory sense organ in many vertebrates. This organ is involved in the Flehmen response and it is necessary for the detection of pheromones, chemical signals released to members of the same species for social and sexual communication. In this review the Authors report on the VNO in dog pointing out the morphogenesis, the structure and the neural pathway toward the central nervous system. By recent immunohistochemical studies it is highlighted that dog VNO neurons express only VR1 genes in their genome, unlike the rodents where VR1 and VR2 genes are expressed. This feature might be the result of VNO regressive process of a macrosmatic mammal, like dog.