On the last two decades, new academic journals, textbook, research networks and key publications attest to ecologists’ rising interest in cities. How did ecologists come to enter cities and to view them as places worthy of studying ? What is the politics of knowledge associated with the rise of ecological research related to cities ? To which extent does this new interest embark a broader redefinition of the type of knowledge that matters in ecology? Drawing on insights by the new political sociology of science, and using a review of programmatic publications in urban ecology, we argue that the politics of urban ecological knowledge does not merely correspond to the promotion of a new subfield of ecology, dedicated to cities: it embarks instead a broader, contested, redefinition of the goals, practices and relevance of ecology as a whole, away from a focus on studying ‘wild’ nature, toward addressing cities as laboratories for exploring social-ecological changes. We unpack the tensions between a ‘city-driven agenda’ aiming to integrate ecological science into the interdisciplinary field of urban sciences, and an ‘ecology-driven agenda’ aiming to research cities as part of ecological discipline.