While the debate on diagnostic disclosure is often based on the premise that knowing about one's condition (the diagnosis and its prognosis) is essential in securing the patient's autonomy, many people with dementia in Korea are not told directly about their diagnosis. This article concerns the laborious and ethically contentious post-diagnostic living undertaken by the families of people with dementia, which I call “living with/out dementia.” This is a paradoxical form of living that has emerged through the increasing biomedicalization of dementia, the socialization of elder care, and an enduring fear of dependency in old age. Attending to how living with/out dementia comes to be initiated and maintained through efforts of care, I argue that nondisclosure entails a kind of ethical process through which dementia is un/done in the caregivers’ struggle to truthfully engage with the person with dementia while actively hiding the diagnostic truth from him or her.