Background: Two hundred and fifty million children under five in low- and middle-income countries are at risk of not achieving their developmental potential. High-quality milestone guides can help mitigate these risks but are often not contextually appropriate for countries like South Africa, because of unavailable resources and its inappropriateness in multilingual group contexts. Aim: This study aimed to develop and pilot a contextually relevant ECD milestone guide for practitioners working with preschool children (3-5 years 11 months) in low-resourced South African communities. Setting: This study focused on ECD practitioners within low-resourced South African communities. Methods: Data collection involved four phases: (1) An initial questionnaire and an abridged milestone guide were reviewed by an expert panel, who suggested contextual adaptations and activities, (2) The Delphi method was used to rank suggestions, (3) Virtual focus group addressed six milestones that required further consensus, (4) a pilot of the language and communication domain was conducted where six practitioners provided feedback on its usability. Results: Practitioners found the milestone guide valuable and usable, supporting their work with young children in low-resourced communities. Feedback informed further refinements to improve usability and contextual relevance. Conclusion: The adapted milestone guide equipped practitioners in low-resourced ECD classrooms with tools to promote age-appropriate development and identify developmental delays early. By addressing these delays, the guide helps break cycles of disadvantage, enabling children to thrive and reach their full potential. Contribution: This study offers a framework for developing contextually relevant milestone guides to support ECD practitioners in low-resourced settings.