The present meta-analysis tested for differences between security of attachment to mothers and fathers. We also analysed associations between security with mothers and fathers. A systematic search in electronic databases identified 95 studies on behavioural measures of attachment to both parents that were included in random-effects meta-analyses. Although security of attachment to fathers was significantly lower than security of attachment to mothers, mean-level differences were very small (g = −0.07). Differences were smaller if more intact families participated. There was a significant correlation of security with mothers and fathers (r = 0.32) and larger associations were found in studies with the Strange Situation rather than the Attachment Q-Set, in studies with older children, and in more recent studies. Further research is recommended on factors that explain observed correlations and mean-level differences.