Objective This study aimed to create and develop a well-designed, theoretically driven, evidence-based, digital, decision Tool to Empower Parental Telling and Talking (TELL Tool) prototype. Methods This developmental study used an inclusive, systematic, and iterative process to formulate a prototype TELL Tool: the first digital decision aid for parents who have children 1 to 16 years of age and used donated gametes or embryos to establish their families. Recommendations from the International Patient Decision Aids Standards Collaboration and from experts in decision aid development, digital health interventions, design thinking, and instructional design guided the process. Results The extensive developmental process incorporated researchers, clinicians, parents, children, and other stakeholders, including donor-conceived adults. We determined the scope and target audience of the decision aid and formed a steering group. During design work, we used the decision-making process model as the guiding framework for selecting content. Parents’ views and decisional needs were incorporated into the prototype through empirical research and review, appraisal, and synthesis of the literature. Clinicians’ perspectives and insights were also incorporated. We used the experiential learning theory to guide the delivery of the content through a digital distribution plan. Following creation of initial content, including storyboards and scripts, an early prototype was redrafted and redesigned based on feedback from the steering group. A final TELL Tool prototype was then developed for alpha testing. Conclusions Detailing our early developmental processes provides transparency that can benefit the donor-conceived community as well as clinicians and researchers, especially those designing digital decision aids. Future research to evaluate the efficacy of the TELL Tool is planned.