Gambling disorder occurs in up to 1% of the U.S. population and was recently re-classified in the DSM-5 as a 'Substance-Related and Addictive Disorder.' The disorder has been characterized by poor perception of risk and increased risk-taking behavior. Such risky behavior in gambling disorder may result from reduced attention to one of several characteristics of the decision making situation: the magnitude of potential rewards or losses, or the probability of winning or losing. Gambling disorder is also characterized by dysregulation of the hypothalamic-pituitary-adrenocortical axis, resulting in lower levels of the hormone cortisol, a primary component of the body's stress response. Better understanding of the relationships among risk perception, risk-taking, and stress physiology could elucidate mechanisms of risky behavior in gambling disorder. We examined the daily pattern of cortisol secretion and risk-taking behavior in 30 individuals with gambling disorder and 30 healthy controls. We assessed these relationships by collecting cortisol samples over two-consecutive days and a battery of laboratory risk perception and risk-taking tasks. Those with gambling disorder showed more risk-taking behavior and blunted diurnal cortisol compared to controls. A conjoint analysis examining behavior relating to rewards, losses, and probabilities did not indicate any differences between gamblers and controls. However, gamblers and healthy controls did not differ on relationships between perception and behavior based on risk information type. Further, gamblers with higher levels of gambling frequency and lower cortisol awakening response had the highest risk-taking behavior. Future research should consider further exploration of risk perception in gambling disorder as a target for treatment.