The rhetoric of the 'best interests of the child' frequently emerges in public and political debates concerning the changing nature of family and society. This article explores how the rhetoric was invoked in recent same-sex marriage debates in Australia. We analyse the public submissions to the 2009 Australian government inquiry into same-sex marriage to reveal the ways in which the abstract figure of 'the child' was deployed. It became evident that heteronormativity was privileged and upheld primarily through the discourse of children's best interests. Concern about the well-being of children raised by lesbian and gay parents was the pivotal argument by those who opposed same-sex marriage. Heteronormativity was reproduced through the claim that same-sex parenting is harmful to children and thus heterosexuality was positioned as the only 'safe' place for parenting. A small number of the submissions in support of same-sex marriage also based their arguments on the best interests of the child. Typically, these submissions positioned lesbian and gay parents as 'just like' heterosexual parents and in doing so they produced an idealised homonormative couple. This unwittingly reinforces heterosexuality through the construction of an 'acceptable' domesticated homosexuality, based on adherence to heteronormativity, which effectively marginalises other family forms and sexual behaviours. We argue that the rhetorical power of the 'best interests' argument relies on the absence of the voices of actual children raised by lesbian and gay parents and that this silencing has harmful consequences for these children.