Mathon-Poinat was originally a secretary, before being elected to the municipal council of La Ricamarie and becoming the first deputy mayor in 2001.
Mathon-Poinat was registered in the Communist Group, as a republican and a citizen and Senators of the Left Party (CRC-GSP). She is a member of the Committee on Constitutional laws, legislation, universal suffrage, regulations, and general administration of the Senate. She is a member of the Delegation for Women's Rights and Equal Opportunities between men and women, and is also a member of the Steering Board of the administrative simplification.