Abstract: Green Public Procurement (GPP) is highlighted as a tool for promoting national environmental protection goals by influencing the demand for products and services. The evolution and characteristics of tendering practices in important sectors and institutional influences on implementation are largely unknown. This study evaluates the effects of recent and ambitious legislative changes on the GPP in the Swiss textile sector from 2018 to 2022. Relying on tender document analysis, it concludes that GPP has increased in tenders issued by organizations subject to the new law. The analysis further highlights the importance of differentiating levels of GPP implementation (“greenness”, “stringency”) to understand GPP evolution. Finally, this study abductively formulates hypotheses about GPP implementation in federal systems. The article emphasizes that analyzing GPP requires an understanding of policy change features and measurements of impacts on GPP at different levels of governance and in different policy domains.