The current study examined the relationship between dispositional optimism and situation awareness. A sample of 77 Royal Norwegian Naval Academy and 57 Royal Norwegian Army Academy cadets were administered the Life Orientation Test prior to participating in a field-training exercise involving a series of challenging missions. Following an infantry mission component of the exercise, situation awareness was measured using the Mission Awareness Rating Scale (MARS), a self-assessment tool. The analysis indicated that dispositional optimism correlated negatively with situation awareness under these conditions. The role of intrapersonal variables in mediating situation awareness and decision-making in stressful situations is discussed.