Assessing interdependence between self and specific others has a rich history in psychological science. Here, we report a novel scale to measure Shared Fate. Studies 1 and 2 (N1 = 198, N2 = 216) show that the Shared Fate scale has two factors assessing perceived shared fate and emotional shared fate with a target, has good reliability (Cronbach’s alpha = 0.81 to 0.91; McDonald’s omega = 0.89 to 0.96), and predicts participants’ willingness to help interdependent others. Studies 3 and 4 (N3 = 695, N4 = 629) indicate that the Shared Fate scale has good discriminant, convergent, concurrent, and predictive validity as well as test-retest reliability across a 14-day period. Taken together, our results suggest that Shared Fate scale is a useful instrument for work on cooperation, interdependence, and social behavior. However, there are still many open questions about the cognitive architecture underlying perceptions of shared fate and how shared fate interacts with genetic relatedness and other sources of fitness interdependence.