Dogs (Canis lupus familiaris), domesticated between 15,000 and 40,000 years ago, exhibit extensive genetic diversity shaped by natural evolution, domestication, and selective breeding. With over 340 recognized breeds, dogs perform diverse roles, from companionship and security to herding, hunting, and biomedical research. Their rapid adaptation to a wide range of ecological conditions highlights their remarkable genetic plasticity and evolutionary success. Advances in high-throughput omics technologies, including genomics, transcriptomics, and proteomics, have identified key genes associated with economically and biologically important traits, such as body size, coat color and texture, cranial morphology, and olfactory sensitivity. Notably, their exceptional sense of smell, regulated by diverse olfactory receptors and neural circuits, underlies their success in scent detection roles, including search and rescue, narcotics, and disease detection. Canine behavioral genetics has uncovered associations between neurotransmitter pathways and specific genetic variants linked to sociability, aggression, anxiety, and trainability. Adaptations to diverse environments such as hypoxia in high-altitude regions, cold climates, and desert environments demonstrate convergent evolution with humans and other species. Additionally, dogs share a high degree of genetic homology with humans and spontaneously develop many of the same diseases, making them valuable preclinical models. Research in canine genetics has contributed significantly to understanding human disorders, including cancer, cardiovascular disorders, and neurological conditions. This review synthesizes current insights into the molecular and genetic mechanisms underlying morphological variation, behavioral phenotypes, disease susceptibility, and environmental adaptability in domestic dogs.