In the context of demographic change, creating a supportive work environment adapted to the abilities and needs of an age-diverse and aging workforce becomes increasingly important. However, implementing HR measures for older workers comes with certain challenges and often fails. Theoretical models and frameworks that depict the hindrances and triggers of implementing HR measures often fail to adequately capture the specific context of aging workforces. Therefore, we aim to identify hindering and facilitating internal and external factors regarding the implementation of HR measures for older workers in particular. Using a reflexive thematic analysis approach, we qualitatively analyzed interview data of organizational stakeholders from 23 different organizations in Germany. We identified various internal organizational factors that can hinder or facilitate the development and implementation of HR measures (e.g., organizational structures, stakeholder support, and resources). Likewise, several external factors were identified that can – depending on their nature and organizational characteristics like size and industry type – influence the development and implementation (e.g., implications of events like the COVID-19 pandemic or social change, legal standards, and external organizations). This study contributes to research and practice on HR measures for older workers by increasing the understanding of diverse hindering and facilitating factors for their implementation, thereby contributing to fostering positive organizational change.