Ageism refers to prejudice and discrimination based on age, often against older people, and based on stereotypical views of older age as a time of frailty, dependence and vulnerability. Across Europe, older people are the most frequent users of healthcare, including hospitals. This paper reports on ageism as one of the themes that emerged from a larger study of hospital social work. Semi-structured interviews and surveys were undertaken with 108 members of hospital social work teams in the UK, exploring their daily practice. Ageism emerged as one of the key themes, as participants challenged what they saw as ageist attitudes from health colleagues, but also from the health and social care system and national government. They simultaneously resorted to ageist generalisations when talking about their own work. We argue that critical gerontology is valuable to underpin hospital social work, but we present evidence that further development is needed to fully align social work practice with critical gerontology. Reflexivity is essential to guard against developing a pervasive view of older people as sick and dependent, based on the inevitably skewed sample of the older population seen by hospital social workers and other healthcare professionals.