Science-Based Targets (SBTs) are being developed for companies to contribute to global sustainability goals, including for ‘nature’. The literature has not yet explored multiple understandings of SBTs. We adopt an interpretive approach, using Q methodology to explore framings of SBTs amongst 22 scientists and practitioners engaged in SBT development. Results show two distinct framings: ‘we need science-based targets to help economic systems move towards global sustainability’ and ‘the system itself is unsustainable and needs to change – science-based targets can help’, with areas of agreement and disagreement. They lean towards reformist or radical discourse, at times weaving them together. What kinds of ‘transformation’, if any, are SBTs capable of driving? Conceptualising SBTs as a boundary object, we suggest that sustainability transformations involve paradoxical tensions, including where actors appeal to the powerful to drive change, but this inhibits the most radical discourses. We conclude with potential implications for sustainability science and governance.