The widespread privileging of children’s voices in recent times has triggered expansion of differing forms of qualitative enquiry that aim to “give children a voice.” Engaging children in research and eliciting their voices on matters that affect them is often showcased as being a more “authentic” way to capture children’s lived realities and afford their agency. Yet, the uptake of voice in qualitative enquiry, and how it may contribute to the privileging of particular ways of knowing (some) children’s lives, is rarely interrogated. Drawing on examples from our own research, in this paper we critically reflect on the frequent invoking of the term voice in qualitative health research with children. In doing so, we challenge claims of authenticity by exposing the tricky epistemological tensions and relations of power that are embedded within the production and legitimation of particular voices as being “correct” ways of knowing about health—including the ways our research intentions and methods contribute to these processes. We reflect on the methodological and epistemological value of silences, dissenting voices and other modes of expression to highlight forms of resistance to adult-led health agendas. We conclude by illustrating how dominant relations of power are (re)produced within and across research spaces, and through the mobilizing or pathologizing of particular young voices through research. Possibilities for advancing ways to harness children’s preferred modes of expression in qualitative research are also considered.