Mothers with severe post‐natal mental illness can be admitted with their infant to a psychiatric mother and baby unit (MBU) in the UK. MBUs provide specialist assessment, management and support. Partners of women admitted to MBUs are integral to their recovery but may show reduced wellbeing themselves, yet their support needs have not been investigated. This study aimed to identify how fathers experience the MBU and how they felt supported. A qualitative design was adopted by using a purposive sample of 17 fathers, recruited from a MBU during their partner's admission. Semi‐structured interviews were used, and responses were analysed using an inductive thematic analysis. Four main themes were developed: (1) ‘double whammy’, (2) understanding the admission and illness, (3) support for fathers, and (4) personal stressors and coping. We identified the emotional struggle that fathers experienced when coping simultaneously with the arrival of a baby and their partner's illness. Furthermore, fathers sought support from many sources, but their knowledge of psychiatric services and mental illness was limited. Fathers felt uncertain about their partners' progression and when their partner would return home with their baby. The provision of an information pack and regular one‐to‐one meetings between fathers and MBU staff are recommended. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Partners of mothers admitted to a psychiatric mother and baby unit have shown increased vulnerability to mental illness themselves; however, little is known about the support that these fathers need and receive during this time. Using interviews, this study sought to understand a) how fathers experienced the mental illness of their partner and the unit's services and b) how fathers could be better supported. Fathers face many emotional and practical challenges during their partner's admission and seek support from numerous sources, including the mother and baby unit. Fathers require more information from the mother and baby unit with regard to mental illness and the unit's services. Furthermore, the introduction of regular one‐to‐one updates between staff and fathers would provide an opportunity for fathers to understand how their partner is progressing and for staff to informally assess the father's wellbeing and outstanding support needs.