Emotional expressions communicate information about the individual’s internal state and evoke responses in others that enable coordinated action. The current work investigated the informative and evocative properties of fear vocalizations in a sample of youth from underserved communities and military veterans while white-water rafting. Video-taped footage of participants rafting through white-water rapids was coded for vocal and facial expressions of fear, amusement, pride, and awe, yielding more than 1,300 coded expressions, which were then related to measures of subjective emotion and cortisol response. Consistent with informative properties of emotional expressions, fear vocalizations were positively and significantly related to facial expressions of fear, subjective reports of fear, and individuals’ cortisol levels measured after the rafting trip. It is important to note that this coherent pattern was unique to fear vocalizations; vocalizations of amusement, pride, and awe were not significantly related to fear expressions in the face, subjective reports of fear, or cortisol levels. Demonstrating the evocative properties of emotional expression, fear vocalizations of individuals appeared to evoke fear vocalizations in other people in their raft, and cortisol levels of individuals within rafts similarly converged at the end of the trip. We discuss how the study of spontaneous emotion expressions in naturalistic settings can help address basic yet controversial questions about emotions.