Disrupted parental sleep, presenting as post-partum fatigue and perceived as problematic infant sleep, is related to increased symptoms of depression and anxiety among new mothers and fathers. Previous research indicates that UK parents would value an approach that facilitates meeting their infants' needs while supporting their own sleep-related well-being throughout their infant's first year. Six initial stakeholder meetings were held with 15 practitioners and 6 parents with an interest in supporting parent-infant sleep needs, to explore existing service provision and identify gaps. The Possums Sleep Program developed and delivered in Brisbane, Australia in a GP clinic setting, was chosen as an appropriate approach. Working collaboratively with a stakeholder group, we translated the Possums Sleep Program into an intervention that could be universally delivered in the UK via NHS antenatal and postnatal practitioners. Parent and practitioner views of the initial materials were obtained via feedback questionnaires and the tool was revised. The intervention was then field-tested by 164 practitioners who delivered it to at least 535 new parents and babies over 5 UK locations, to capture anonymous parent and practitioner views of the intervention concept, the materials, and their experiences with both. The intervention helps parents recalibrate their expectations of infant sleep development, encourages responsive parenting and experimentation to meet their infant's needs, offers parents strategies for supporting the development of their babies' biological sleep regulators and promote their own well-being, and teaches parents to manage negative thinking and anxiety that can impede sleep using the principles of Acceptance and Commitment Therapy. The 'Sleep, Baby & You' discussion tool, a 14 page illustrated booklet for parents, was field-tested and evaluated by practitioners and parents who offered enthusiastic feedback. Practitioners reported the 'Sleep, Baby & You' materials were easy for them to explain and for parents to understand, and were a good fit with the responsive parenting approaches they employed in other areas of their work. Parents who received the intervention postnatally understood the material and found the suggestions easy to follow. All parents who provided feedback had implemented one or more of the suggested changes, with the majority of changes (70%) being sustained for at least two weeks. Practitioners recommended development of digital and antenatal versions and offered feedback on circumstances that might challenge effective uptake of the intervention. 'Sleep, Baby & You' is a promising tool for promoting parental attitude and behaviour-change, that aims to adjust parental expectations and reduce negative thinking around infant sleep, promote responsive infant care in the face of infant-related sleep disruption and fatigue, and support parental well-being during the first year of parenthood. Initial field-testing provided insights useful for further development and subsequent testing via a randomised trial. Support exists for incorporating 'Sleep, Baby & You' into an anticipatory, universal intervention to support parents who may experience post-partum fatigue and infant sleep disruption.