BACKGROUND: Health care professionals play a central role in offering reproductive genetic carrier screening but face challenges when integrating the offer into practice. The aim of this study was to design, execute, and evaluate theory-informed implementation strategies to support health care professionals in offering carrier screening. METHODS: An exploratory multi-method approach was systematically employed based on the Theoretical Domain Framework (TDF). Implementation strategies were designed by aligning TDF barriers reported by health care professionals involved in a large carrier screening study, to behaviour change techniques combined with study genetic counsellors' experiential knowledge. The strategies were trialled with a subset of health care professionals and evaluated against controls, using findings from questionnaires and interviews with healthcare professionals. The primary outcome measure was the number of couples who initiated enrolment. RESULTS: Health care professionals (n = 151) reported barriers in the TDF Domains of skills, e.g., lack of practice in offering screening, and challenges of environmental context and resources, e.g., lack of time, which informed the design of a skills video and a waiting room poster using the TDF-behaviour change technique linking tool. Following implementation, (Skills video n = 29 vs control n = 31 and Poster n = 46 vs control n = 34) TDF barrier scores decreased across all groups and little change was observed in the primary outcome measure. The skills video, though welcomed by health care professionals, was reportedly too long at seven minutes. The waiting room poster was seen as easily implementable. CONCLUSIONS: As carrier screening moves towards mainstream healthcare, health care professionals report barriers to offering screening. To meet their needs, developing and testing experiential and theory-informed strategies that acknowledge contextual factors are essential.