From the docs:
TDE and In-Memory OLTP
You can enable TDE on a database that has In-Memory OLTP objects. In SQL Server 2016 (13.x) and Azure SQL Database, In-Memory OLTP log records and data are encrypted if you enable TDE. In SQL Server 2014 (12.x), In-Memory OLTP log records are encrypted if you enable TDE, but files in the MEMORY_OPTIMIZED_DATA filegroup are unencrypted.