This paper explores contemporary approaches to balancing truth with the provision of hope during the disclosure of a dementia diagnosis. We discuss the ethical significance of these practices as they relate to each member of the triad – the person, the carer and the clinician – at the point of diagnosis and beyond. The process of disclosing a diagnosis of dementia is complex. It encompasses breaking bad news while balancing hope, with truth about a progressive life-limiting condition. The process of receiving the diagnosis likewise challenges the person who may be unprepared for the diagnosis, while carers seek information and supports. The impact of receiving a diagnosis of dementia can be life-changing and harmful at the personal level – for both the person and carer. This risk of harm becomes a critical consideration for clinicians when deciding on the level of truth: what information should be relayed and to whom? That risk is also balanced against the ethical issue of patient autonomy, which includes the right to know (or not) and make informed decisions about therapeutic interventions. While the consensus is that the autonomy of the person living with dementia must be upheld, controversy exists regarding the extent to which this should occur. For instance, at diagnosis, it is common for clinicians to use euphemisms rather than the word dementia to maintain hope, even though people and carers prefer to know the diagnosis. This practice of therapeutic lying is a pervasive ethical issue in dementia care, made more acceptable by its roots in diagnosis disclosure.