Agrifood related social controversies tend to involve scientific issues and advocacy groups increasingly turn to citizen science (CS), participatory data taking by regular people, to produce health and environmental data. A common assumption is that CS’s value lies in the data produced, and its volume and quality decide its persuasive power. This article describes participatory monitoring of genetically engineered rapeseed (canola) in Japan to suggest that social movements can leverage CS not only for the production of scientific data but also as occasions for recruitment, political awareness-raising, and collaboration with other civic organizations. The article proposes a new framework for understanding CS–social movement relations that is multi-actor (vs. expert–laypeople dyad); process-oriented (vs. product/data-oriented); and long-term (vs. one-shot and isolated data taking). There is an increasing awareness of the diversity of CS. Even those that are led by grassroots organizations have multiple and shifting uses of data and foster varying political subjectivity among participants. The proposed framework helps to understand the dynamics that shape such heterogeneous pathways of CS.