This paper outlines the full details of Lucretius’ treatment of parental love. It shows that Lucretius is faithful to Epicurus’ notorious claim that parental love is not natural: in addition to orthodox Epicurean hedonist concerns, Lucretius asserts that children do not ‘belong to’ their parents by nature; as such, even though parental love is now ubiquitous and indeed a cultural norm, there is no basis for the naturalness of parental love. This model of the relationship between parents and children does not, however, apply in the case of certain animals, who do have natural parental love for their offspring. Focussing on two famous scenes, the sacrifice of Iphigenia and the forlorn heifer seeking her sacrificed calf, the paper argues that, by highlighting the fragility of human parental love in comparison to that of the animals, Lucretius brings to his Roman readers’ attention the relative weakness of the familial ties that bond human beings together. At the same time, he emphasises the need to maintain these ties, if social and political concord, with all its benefits, is to continue. It transpires that unlocking the details of Lucretius’ treatment of parental love brings a key lesson of the poem into clearer focus.