Mattfeldt first became a member of the Bundestag in the
2009 German federal election, representing the
Osterholz – Verden district. In parliament, Mattfeldt is a member of the Committee on Petitions, the Budget Committee and its Subcommittee on European Affairs. On the Budget Committee, he serves as his parliamentary group’s
rapporteur on the
annual budget of the
Federal Ministry for Economic Affairs and Energy and the
Federal Ministry of Defence. Since 2024, he has also been a member of the so-called
Confidential Committee (
Vertrauensgremium) of the Budget Committee, which provides budgetary supervision for Germany's three intelligence services,
BND,
BfV and
MAD. == Political positions ==