Risk assessment (RA) is an evolved, generally adaptive, mechanism comprising focused attention and appraisal of potential threat stimuli and situations. Initially characterized in animal models, it provides a number of behavioral and functional parallels to patterns of rumination, gaze biases, and other forms of affective cognition that appear to be disregulated in depression and anxiety. Serotonergic mechanisms are involved in these mood disorders, and an emerging body of evidence suggests that they may modulate the affective cognitive changes common to such psychopathologies. Findings of parallel effects of serotonin systems in RA would support a view that it may provide a useful behavioral endophenotype for translational research on mood disorders. This review examines the involvement of serotonergic mechanisms in both animal models of RA, and in an array of tasks focusing on affective cognitive changes in individuals with depression or anxiety. Results suggest substantial serotonin involvement in both RA behaviors measured in rats or mice, and in the "intersection of emotional and cognitive processes"  in people.