Stress, when it becomes chronic and when it impacts the wellbeing of an animal, has a negative influence on physical and mental health and can cause changes in behavior in reptiles in the wildness as well as in those kept as pets. The stress response is made of the autonomic nervous system response, neuroendocrine response, immune response, and behavior change. Stress in reptiles in the wildness is affected by the availability of finding food, the presence of predators, environmental factors, and anthropological influences. At captive reptiles kept as pets the greatest source of stress is inappropriate menagament and inadequate conditions in which animals are kept due to poor education of the owners. The need for a standardized quantificational method for precise measurement of stress level still exists, but momentarily the most suitable biomarker of chronic stress is the level of corticosterone in plasma, feces, or shed skin. If the stress in captive reptiles is correctly evaluated and treated, their health and wellbeing can be improved. In the presented thesis, beside mechanism and influence of stress on reptiles, appropriate menagement conditions for keeping reptiles in captivity are described as well as some of the most frequent illnesses that veterinarians encounter as a consequence of stress.