The past two decades witnessed an increasing interest in literary worldmaking. This paper begins with examining the current models of worldmaking, in particular, the model of the phenomenological, the constructive, the cognitive psychological, the media, the narratological, and the ethical. In doing so, it reveals their shared feature of the human-centred view and mimetic bias. Against the backdrop of the non-human turn in the 21st century, it questions the generally accepted assumption that “the representation of human experience is the central aim of narrative” (Fludernik 1996: 51) and gears scholarly attention to non-human agents in literature and their contribution to constructing the non-human world. Drawing on insights from unnatural narratology, it aims to go beyond the existing mimetic paradigm by proposing the unnatural ways of worldmaking. Taking cues of the narrative function of worldmaking and focusing on the non-human character in particular, it delves into three types of non-human worlds in Ian McEwan’s fiction, namely the world of a fetus in The Nutshell (2016), the world of a machine in Machines Like Me (2019), and the world of a metamorphosized being in The Cockroach (2019). Arguably, by projecting the non-human world and representing the non-human experience, unnatural narrative works invite readers to address such questions as what to do with non-human world, how it is made, and ultimately what it means to humans.