Modern zoos and aquariums are defined by several primary goals, which include improving the welfare of their animals, public education, and inspiring visitors to develop an interest in conservation. Animal-Visitor Interactions (AVIs) (i.e., the impact of captive animals and visitors on each other) are a primary means to study these goals. The introduction of new animals into two seal exhibits—the harbor and northern fur seals—at the Seattle Aquarium presented a valuable opportunity to assess the impacts of introductions on the currently exhibited animals and aquarium visitors. The impacts of animal introductions were measured through direct observations of seal activity (i.e., ethogram behavioral observations) and visitor activity (i.e., crowd size and visitor length of stay) before and after new seal introductions. This study consisted of two experiments: Experiment 1 (Harbor seal exhibit) and Experiment 2 (Northern fur seal exhibit). In Experiment 1, we found that the introduction had few impacts on the existing harbor seals or on visitor activity. In Experiment 2, the introduction of a new fur seal had significant positive impacts on the existing fur seal, as was seen through increased social behaviors and decreased stereotypic behaviors, as well as a significant increase in crowd size post-introduction. Based on these findings, new animal introductions were associated with neutral to positive changes in both seal and visitor activity. Findings from this study suggest that studying new animal introductions can result in better understanding and promoting positive interactions with existing animals (introduction effects) and likewise positive experiences for zoo and aquarium visitors (introduction experiences).