Humanitarian crises often garner attention in national and international media. After a crisis, the work of long-term development takes over. International non-government organizations play a crucial role in the long-term development projects that provide aid and services around the world. One sub-set of these organizations includes the primarily volunteer-based organizations that sponsor groups to travel on short-term medical trips. During these trips, groups from the United States travel to a foreign country and usually work on construction projects, provide orphan care, deliver medical services, or implement environmental improvement initiatives. These groups affect how organizations engage with their beneficiaries in overseas locations. My dissertation explains how group styles affect engagement with beneficiaries. A group styles approach explains how the group customs shape their engagement with beneficiaries and with each other. As many of these groups are faith-based, this dissertation also considers how group styles affect the influence of religion in humanitarian development. At another critical juncture, group styles mediate the relationship between humanitarian discourses and groups' engagement in cross-cultural settings. A focus on the group and scene styles of humanitarian aid shows how customs matter, incorporates contextual specificity, and allows for comparative analysis across multiple contexts.