Children often fail to control variables when conducting testsof hypotheses, yielding confounded evidence. We propose thatgetting children to think of alternative possibilities throughcounterfactual prompts may scaffold their ability to controlvariables, by engaging them in an imagined intervention that isstructurally similar to controlled actions in scientificexperiments. Findings provide preliminary support for thishypothesis. Seven- to 10-year-olds who were prompted to thinkcounterfactually showed better performance on post-testcontrol of variables tasks than children who were given controlprompts. These results inform debates about the contributionof counterfactual reasoning to scientific reasoning, and suggestthat counterfactual prompts may be useful in science learningcontexts.