Teacher involvement in the design of curriculum materials is expected to facilitate the process of implementing an educational reform, especially when teams of teachers collaborate in Teacher Design Teams (TDTs). However, little is known about the implementation activities that provide opportunities to develop teachers’ curriculum design expertise. The implementation activities of three TDTs that renewed their foreign language curriculum were investigated using a case study approach. The results showed that although TDTs carried out a wide variety of activities to foster classroom implementation, classroom use of the new curriculum materials varied. The need for additional support for TDTs in the implementation process in order to successfully facilitate changes in teachers’ classroom practices is discussed. https://link.springer.com/chapter/10.1007/978-3-030-20062-6_10