A rainstorm disaster occurred on July 20, 2021 in the Henan Province, China, posing a severe threat to residents' lives and property. During this period, the victims engaged in shadow evacuation behaviors-that is, people who had not received official evacuation instructions or were not in the designated evacuation areas chose to spontaneously evacuate. Social capital refers to resources acquired or mobilized through social connections and relationships; it is a significant factor during all stages of natural disasters. We investigated the relationship between social capital and shadow evacuation. A total of 290 questionnaires were obtained from Fengquan and Weihui in Xinxiang City, Henan Province, China. The collected data were analyzed using descriptive statistics, confirmatory factor analysis, and binary logistic regression analysis using SPSS. The results showed that bonding social capital (p = 0.037 < 0.05, B = 0.347), bridging social capital (p = 0.003 < 0.01, B = 0.520), and linking social capital (p = 0.014 < 0.05, B = 0.390) had significant positive impacts on shadow evacuation behavior. The control variables of living with the disabled or elderly (p = 0.003 < 0.01, B = 0.989) and disaster experience (p = 0.000 < 0.01, B = 1.250) also had positive impacts on shadow evacuation behavior; the demographic variables had a limited impact.