The purpose of this mixed methods systematic review was to identify factors associated with anticipatory grief, post-death grief, and prolonged grief in informal carers of people living with Motor Neuron Disease (MND) to inform future research and practice. Six electronic databases were searched and two quantitative and eight qualitative studies were identified. Five overarching themes were generated through thematic synthesis. The findings suggest that there are factors that may affect different grieving processes. It might be particularly important to target some factors prior and after the death of the person living with MND such as the knowledge about the progression of the disease, changes in relationships, anxiety and depressive symptoms of carers, and planning for death of the care recipient. Factors that may affect all three grieving processes were also identified such as negative experiences of caregiving, experiences of losses, end of life and psychological support, and emotional avoidance coping.