We tested the hypothesis that dormancy generates a seed bank of protected individuals that can modify antagonistic coevolutionary dynamics. We experimentally evolved a spore-forming bacterial host (Bacillus subtilis) or its non-spore-forming derivative, along with a phage (SPO1) that can infect active but not dormant cells. Using pooled population sequencing of longitudinal samples, we quantified patterns of molecular diversity and genetic signatures of coevolution.