The application of remote sensing in scientific research and operational fields is rapidly increasing. Over the past decade, the use of unmanned aerial vehicles (UAVs) for remote sensing has reached a significant stage of development. The diverse applications of this technology have created new opportunities for precision and smart agriculture. One of the key challenges in advanced agriculture is the measurement and monitoring of biological stresses in trees, including water stress, nutrient stress, and biotic stress caused by pests and diseases. By identifying and managing these stresses, orchard managers can reduce damage, predict yields, and optimize production practices. Consequently, UAV-based remote sensing systems are increasingly replacing traditional methods for assessing biological stresses in orchards. Given the global scope of research in this area, there is a clear need to synthesize existing findings, identify research gaps, and provide technical recommendations for practical applications. This study presents the first comprehensive review of research on UAV-based monitoring of biological stresses in orchard trees, based on studies retrieved from reliable citation databases. The review analyzes active countries, tree species, monitored parameters, UAV platforms, sensors, data analysis methods, as well as the advantages and limitations of UAV-based monitoring. The findings of this study provide a valuable reference for researchers, practitioners, and decision-makers in the field.