The introduction of biomarkers and precision diagnostics has revolutionized animal health monitoring. Biomarkers are measurable biological characteristics that provide insight into physiological status, disease progression, immune responses, and therapeutic outcomes in animals. Advances in veterinary medicine have expanded the use of molecular and physiological biomarkers, including genomic, proteomic, metabolomic, and immunological indicators, enabling earlier and more accurate disease diagnosis. The rapid development of high-throughput omics technologies, biosensors, wearable devices, artificial intelligence (AI), and machine learning has further enhanced diagnostic sensitivity and specificity. These technologies facilitate real-time health monitoring, evidence-based disease management, and improved productivity, animal welfare, and sustainability in livestock and companion animals. Precision diagnostics integrates multidimensional biological data to generate disease-specific signatures, reducing reliance on traditional symptom-based diagnosis and supporting targeted interventions. Furthermore, combining genomics, proteomics, metabolomics, and digital health indicators has improved disease prediction and risk assessment. Despite these advances, important challenges remain, including biomarker validation, standardization of analytical methods, data governance, ethical considerations, and the cost-effectiveness of emerging technologies. Future research is expected to focus on integrated multi-omics platforms, AI-driven diagnostic systems, portable biosensing technologies, and personalized veterinary medicine. Together, these innovations have the potential to transform animal healthcare by enabling proactive disease surveillance, accurate diagnosis, and evidence-based clinical decision-making. This review summarizes recent advances in biomarkers and precision diagnostics, discusses current challenges, and highlights future perspectives for improving animal health monitoring and modern veterinary practice.