A range of professionals and services are often involved in supporting parents with mental health needs where there are child protection concerns. However, they do not always meet the needs of this population who tend to experience inadequate support and mistrust of services. This review aimed to synthesize parent and practitioner experiences of support for parents with both mental health needs and children’s social services involvement. We performed electronic searches of the following databases: PsycINFO, CINAHL, HMIC, MEDLINE, Embase, Social Policy and Practice, Social Services Abstracts, Social Science Citation Index, OpenGrey, Social Care Online, and ProQuest. Following searching and screening, 41 studies were identified including 359 parents and 1370 practitioners. We worked with a Lived Experience Advisory Group to develop the following themes: (1) a downward spiral of service intervention; (2) working with parents, not against them; (3) support wanted versus support provided; and (4) constrained by service rigidity. We found that families were often parenting amidst trauma and adversity. However, service involvement could trigger a “downward spiral” of stressful processes over which parents felt they lacked control. Instead of improving their situations, support sometimes added to families’ difficulties, worsening parents’ mental health and making them feel marginalised, criticised, and retraumatised. There were, however, also examples of positive practice, where practitioners and parents developed trusting, open, and mutually respectful relationships. Practitioners often felt that they were limited in their ability to offer collaborative, holistic care because services were fragmented, underfunded, crisis driven, and inflexible. Difficulties mentioned most often by parents, such as financial issues, tended not to be a focus of available interventions. We conclude that the key issues identified must be targeted to improve support.