Acquired brain injury (ABI) represents a great burden for not only the person with ABI but also their partner. Grief among partners of adults with ABI is a broadly recognized phenomenon. However, few studies have examined partners’ experience of grief, and little is known about grief as a reaction to ambiguous loss. This article presents a phenomenological study that aimed to explore the experience of grief among caregiving partners. Four semi-structured interviews were conducted and analyzed by a phenomenological descriptive analysis. Through the analysis, nine themes were identified: the process of becoming a caregiver, grief emotions, loss, emotionally closer relations to the partner relations, dyadic coping, unmet needs for support, future opportunities, changes over the life course, and understanding of grief. The themes are interrelated and highlight various aspects of the phenomenon of grief as experienced by caregivers. Results reveal that grief is often a reaction to ambiguous loss and is experienced as disenfranchised. Furthermore, the study indicates that caregivers’ perception of grief and the situation in general were essential to the experience of grief.