Non-Governmental Organizations (NGOs) in the field of international development are increasingly adopting so-called managerial working methods. This article explores the changing belief systems and practices of Northern development NGOs as well as the strains arising from this adoption. We draw upon a literature review and case studies of two Northern development NGOs and their Southern counterparts in Ghana, India and Nicaragua. Our findings show that managerialist ideas and practices clash with a number of values, views and goals that “traditionally” have been widely shared in the private aid channel. To ensure that their actual practices remain consistent with their belief systems, Northern development NGOs cannot avoid making tough choices that will have key consequences for their future relevance and identity. Copyright © 2013 John Wiley & Sons, Ltd.