Reproductive health and mental health are intertwined, but studies investigating family planning needs and desire for children in mental healthcare are scarce. We studied the experiences of (former) patients, those with close relationships with the (former) patients (close ones) and mental health professionals (MHP) on discussing family planning and desire for children in mental healthcare. We combined quantitative (two nationwide surveys) and qualitative data (four focus groups) in a mixed-methods approach with sequential analytical design. Combined data from focus groups (n = 19 participants) and two surveys (n = 139 MHPs and n = 294 (former) patients and close ones) showed that a considerable group of MHPs (64.0%), patients (40.9%) and close ones (50.0%) found that family planning should be discussed by a psychiatrist. However, several obstacles impeded a conversation, such as fear of judgment, lack of time and knowledge and limited opportunity for in-depth exploration of life themes in therapeutic relationships. To increase the autonomy of patients in discussing family planning, we suggest MHPs explore the desire to discuss family planning with all patients in the reproductive phase of life, prior to discussing contraceptive care. MHPs should receive education about psychiatric vulnerability in relation to family planning and desire for children, and patients and close ones should be empowered to initiate a conversation themselves.