<p>The application of discrete choice experiments (DCEs) is gaining popularity as a means of exploring preferences on health-related issues. The quality and validity of DCEs largely depend on the formative phase of attribute development. This paper documents a systematic attribute development process for a DCE assessing preferences for long-acting HIV prevention products among pregnant and breastfeeding women (PBFW) in Kenya. We applied the Helter and Boehler four-stage attribute development framework, comprising raw data collection, data reduction, removal of inappropriate attributes, and appropriate wording. Through literature review and qualitative approaches, we identified twelve attributes for products formulated as oral tablets, injections, vaginal rings, and implants. Six of the twelve attributes were considered plausible, salient, and capable of being traded, namely dosing frequency, effectiveness in HIV prevention, ability to prevent pregnancy, ability to prevent sexually transmitted infections, product access location, and product cost. A pilot among thirty PBFW confirmed the clarity and relevance of the six attributes, informing their inclusion in the DCE. Documenting this transparent step-by-step process improves transparency and facilitates objective evaluation of the DCE’s formative phase. These findings contribute to methodological rigour in DCE design and provide empirical evidence for expanding preference-based HIV prevention strategies that will benefit PBFW.</p>