Purpose: Oncofertility care at cancer diagnosis remains underimplemented across oncology and fertility care settings, with limited tools to scale up effective implementation strategies. Using implementation science theory, we systematically assessed factors that influence oncofertility care implementation and mapped scalable strategies, particularly electronic health record (EHR)-enabled ones, that fit adult and pediatric oncology care contexts. Methods: Using purposeful sampling, we recruited health care providers and female, reproductive-aged survivors of adolescent and young adult (AYA) cancers (AYA survivors) from a comprehensive cancer center and a freestanding children's hospital to semistructured interviews and focus groups. Using thematic analysis combining inductive codes with deductive codes using the Consolidated Framework for Implementation Research (CFIR), we characterized barriers and facilitators to care and designed responsive strategies. Two coders independently coded each transcript. Results: We recruited 19 oncology and fertility providers and 9 cancer survivors. We identified barriers and facilitators to oncofertility care in the CFIR domains of individual, inner setting, outer setting, and process, allowing us to conceptualize oncofertility care to encompass three core components (screening, referral, and fertility preservation counseling) and map five strategies to these components that fit an adult and a children's context and bridge oncology and fertility practices. The strategies were screening using a best practice advisory, referral order, telehealth fertility counseling, provider audit and feedback, and provider education. All but provider education were EHR tools with embedded efficiencies. Conclusion: An implementation science approach systematically assessed oncofertility care and mapped strategies to provide a theory-based approach and scalable EHR tools to support wider dissemination.