Comparison has been shown to aid children's immediate learning across a variety of domains. However, less research has examined the effects of comparison on children's long-term memory, particularly in the laboratory setting. This study examined what children remember about science concepts using comparison. Experiment 1 (N = 120
59 boys) taught children aged 4 to 8 years about animal adaptation using comparison and then tested their memory or generalization immediately or after a 5-minute delay. Experiment 2 (N = 120
56 boys) taught children about animal adaptation in the same way, but prompted children to generalize only perceptual or relational information at test. Results revealed that children do not rapidly forget information after a brief delay, but they struggle to generalize both perceptual (β = -.527, p <
.001) and relational (β = -.496, p <
.001) information immediately and over time, and that using language prompts may help to mitigate this effect, particularly with relational information (β = .236, p = .005). In sum, these experiments suggest that children are able to retain information after a brief delay, that additional cognitive supports are likely needed to facilitate long-term learning from comparison, and that language is a promising way to support this learning.