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Despite the fact that parasite dispersal is likely to be one of the most important processes influencing the dynamics and coevolution of host‐parasite interactions, little information is available on the factors that affect it. In most cases, opportunities for parasite dispersal should be closely linked to host biology. Here we use microsatellite genetic markers to compare the population structure and dispersal of two host races of the seabird tick Ixodes uriae at the scale of the North Atlantic. Interestingly, tick populations showed high within‐population genetic variation and relatively low population differentiation. However, gene flow at different spatial scales seemed to depend on the host species exploited. The black‐legged kittiwake (Rissa tridactyla) had structured tick populations showing patterns of isolation by distance, whereas tick populations of the Atlantic puffin (Fratercula arctica) were only weakly structured at …