Informal carers play a vital role in supporting Australians living with a mental illness, including during the acute phases of illness; however, little is known about their impact on length of hospital stay. We aimed to investigate the impact of having a carer and of carer burden on length of hospital stay for mental health. Two Australian datasets were used. Data from the 2010 National Survey of High Impact Psychosis (n = 1825) were used to investigate the impact of having versus not having a carer on length of hospital stay for mental health.