After finishing gymnasium-b in 's-Hertogenbosch in 1975, Vos went on to study biology at the University of Wageningen, being graduated in 1983. During her study she was active in the students movement, the peace movement and the campaign against nuclear energy. In 1984 she worked as teacher and campaigner for an environmental organisation, 'Milieudefensie' ('Defense of the Environment'). In 1990 she began to teach ecology at the Centre of Ecology of the University of Leiden until 1992. In 1989 she had become a member of the GreenLeft and almost immediately entered its temporary board, that would oversee the merger of the four parties that would form the GreenLeft. She was elected party chairperson in 1990. In 1992 this office became a paid office and she left the university.
In 1994 she was asked to become a stand (?) on the GreenLeft list of candidates. She was elected in 1994 to the lower house of parliament. Between 1995 and 1996 Vos was chairperson of the parliamentary commission on climate change. In 1997 she was elected animal rights protector of the year. Since 1998 Vos has been deputy party leader. In 2003 she was interim party leader, when Femke Halsema gave birth to twins. Between 2001 and 2003 she was chairperson of the parliamentary commission on fraud in the building sector. In 2003 she became member of the board of advice of the refugee-assistance organisation 'Steunpunt Vluchteling' ('Supportpillar for Refugees'). In 2004 she announced that she would not enter in the next general election, instead she would become alderwoman in Amsterdam, if the GreenLeft enter local government there.
Since 2004 Vos is co-owner of vineyard in southern France, the vineyard produces organic wine, sunflowers and grain.
While still in parliament, Vos played an important role in the election campaign and government formation in Amsterdam. In the March 2006 local elections Marijke Vos had a lijstduwers position on the GreenLeft list for the city council of Amsterdam, she was elected by a large number of preference votes. In April 2006 she was appointed alderwoman in Amsterdam in a PvdA/GreenLeft coalition. On May 23, 2006 she left parliament to devote herself to her alderman's work, she will be succeeded by former GreenLeft vice-chair, Nevin Özütok.