There are a number of research fields that exhibit a special connection to some particular activist movement. Typically in these cases, we observe a remarkable degree of personnel overlap between the movements and the scientific communities. I have two primary aims. First, I shall explore the reasons why there are such close entanglements between some research fields and some activist movements. I argue that both scientists and activists have specific epistemic interests that help explain why both practices tend to intersect functionally. Second, I shall evaluate these entanglements from an epistemological point of view. Drawing on a conception of science that has science consisting of two essential tasks—asking significant questions and adequately answering them—, I argue that activists’ contribution to science is ambivalent with regard to the first task because they can help to overcome the unjust distribution of resources, but they can also be the source of new inequalities. Regarding the second task, I similarly suggest that activists can serve a useful purpose in science, since they tend to exhibit certain epistemically valuable properties and can help compensate for what I call collective biases, although in certain situations they tend to reinforce collective biases.