Against the background of demographic change and skills shortage, human resource management needs to adopt organizational practices for an aging workforce in many countries around the globe. The Later Life Workplace Index (LLWI) is a nine-domain measurement tool that assesses such practices. We validate the LLWI across 17 countries – namely Belgium, Bulgaria, Brazil, the Czech Republic, Denmark, India, Israel, Italy, Japan, Korea, Lithuania, the Netherlands, Poland, Portugal, Romania, Slovakia, and Türkiye – representing diverse cultural and institutional contexts. Data were collected between 2019 and 2025 with an average sample size of 320 participants per country, resulting in 5,444 participants. The 80-item LLWI was translated from German or English to the respective target languages using a back-translation technique. We first assessed the measurement model with a CFA and determined convergent, discriminant, criterion, and predictive validity for each country. Then we conducted a multi-group CFA for cross-country analysis. Findings largely support the validity and applicability of the LLWI on the country level, although some country-specific variations warrant further investigation. Measurement invariance analysis provides evidence that the LLWI is suitable for cross-country comparisons. By validating the LLWI across 17 countries, this study has the potential to offer a foundational contribution to international HRM research.