The paper develops a critical reflection upon the methodological and ethical challenges of researching the food practices of low-income families with children. We draw on data and fieldwork experience in Portugal, within a recently completed European research project. The study aimed to understand children's experiences and views about the place of food in their lives, drawing on sociological approaches to childhood that conceptualize children as social agents, active participants within families and competent experts on their own social and interactional worlds. These assertions underlie the project's mixed-method approach (in-person interviews, questionnaires and photo-elicitation). We argue that beyond well-known ethical challenges (such as gatekeeping, power asymmetries, reciprocity and active participation), food and food poverty bring forth unique dilemmas, which may affect children's participation in research. Following the dimensions suggested by Tracy, our contribution offers a reflexive account of ethics-in-practice of how we dealt with ethical dilemmas on the field.