Mona Keijzer began her career in January 1991 as a legal policy officer serving the municipality of Waterland. From 1993 to 1994 she was a management trainee at Leiden University. She then held legal positions at the Gelderland Environment Inspectorate and the municipality of Almere. In 1998 Keijzer became a member of the municipal executive and deputy mayor of the municipality of Waterland. In 2006 she began working as a lawyer and certified mediator at the law firm Abma Schreurs Advocaten en Notarissen in Purmerend. In 2007 she became a member of the Purmerend municipal executive. In 2012 Keijzer became a member of parliament for the Christian Democratic Alliance (CDA), with policy responsibility for chronic care for older and disabled people, and later became spokesperson for hospital care and asylum, migration and integration policy. On 26 October 2017 Keijzer was appointed State Secretary for Economic Affairs and Climate Policy in the third Rutte government.