We assessed the degree of similarity between signature whistles of mother and offspring pairs in free-living Atlantic spotted dolphins (Stenella frontalis). As a means of qualitative evaluation, judges compared the time-frequency contour patterns of signature whistle spectrograms. We also evaluated quantitative measurements of whistle frequency and duration. All five female offspring produced signature whistles that were similar to their mothers’ whistles by a least one means of comparison, whereas two of the four male offspring produced signature whistles that were dissimilar from their mothers’ by both methods of comparison. However, statistically, male offspring were just as likely to produce signature whistles like their mothers’ as female offspring (p = 0.167). We compared whistle similarity between mothers and offspring to the degree of association for each pair. Offspring that most often associated with their mothers when they were four years of age had whistles that were more similar to their mothers’ whistles both qualitatively (r(4) = 0.92, p = 0.009) and quantitatively (r(4) = 0.92, p = 0.004). Because signature whistles are developed within a dolphin’s first year, our finding likely reflects the level of bond between mother and calf.