Serious illness conversations aim to align the care process with the goals and preferences of adult patients suffering from any advanced disease. They represent a challenge for healthcare professionals and require specific skills. Conversation guides consistent with task-centered instructional strategies may be particularly helpful to improve the quality of communication. This study aims to develop, validate, and preliminarily evaluate an educational booklet to support Italian social and healthcare professionals in serious illness conversations. A three-step approach, including development, validation, and evaluation, was followed. A co-creation process with meaningful stakeholders led to the development of the booklet, validated by 15 experts on clarity, completeness, coherence, and relevance. It underwent testing on readability (Gulpease index, 0 = lowest-100 = maximum) and design (Baker Able Leaflet Design criteria, 0 = worst to 32 = best). Twenty-two professionals with different scope of practice and care settings evaluated acceptability (acceptable if score ≥30), usefulness, feasibility to use (1 = not at all to 10 = extremely), and perceived acquired knowledge (1 = not at all to 5 = extremely). After four rounds of adjustments, the booklet scored 97% for relevance, 60 for readability, and 25/32 for design. In all, 18 (81.8%), 19 (86.4%) and 17 (77.3%) professionals deemed the booklet acceptable, moderate to highly useful, and feasible to use, respectively; 18/22 perceived gain in knowledge and all would recommend it to colleagues. The booklet has good readability, excellent design, high content validity, and a high degree of perceived usefulness and acquired knowledge. The booklet is tailored to users' priorities, mirrors their most frequent daily practice challenges, and offers 1-minute, 2-minute and 5-minute solutions for each scenario. The co-creation process ensured the development of an educational resource that could be useful regardless of the scope of practice and the care setting to support professionals in serious illness conversations.