We compared the underwater vocalizations of harp seals Pagophilus groenlandicus Erxleben, 1777 recorded during the breeding season at three locations: Jan Mayen Island (north of Iceland); Gulf of St Lawrence; and the ‘Front’ ice east of Labrador. The three herds shared 17 call types. The Jan Mayen herd had one call type not found in the Gulf or Front. One of the Gulf and Front call types was not found at Jan Mayen. Based on ANOVA post hoc pairwise comparisons between locations, the three herds exhibited a similar number of within-call type differences in duration, number of elements, start pitch and end pitch. There were no differences in proportional usage of call types between the Gulf and Front herds but both differed in a similar manner from those of the Jan Mayen herd. These findings support tagging studies that indicate that the Gulf and Front herds may be interbreeding and both are reproductively isolated from the Jan Mayen herd. We found no evidence of acoustic adaptation to the site-specific ice and environmental conditions associated with the three study locations.