Martina Gedeck was born 14 September 1961 in Munich, West Germany and grew up in Bavaria, the oldest of three girls. In 1971, her family moved to Berlin, where the eleven-year-old debuted as an Actress in children's television shows.

After graduating school in 1981, she enrolled at the Free University of Berlin, majoring in German Literature and History. From 1982 to 1986, Martina attended acting classes at the Berlin University of the Arts. During that time, she made her stage debut at the Theater am Turm in Frankfurt. Gedeck performed regularly at the Deutsches Schauspielhaus in Hamburg, and appeared in plays in Basel, Berlin, Frankfurt, and Hamburg.

In 1994, Gedeck gained the attention of film audiences with her performance in Sönke Wortmann's hit comedy Maybe... Maybe Not (Der bewegte Mann). In 1995, Gedeck received critical praise for her award-winning performance in the television drama Hölleisengretl (de). In 1997, she furthered her reputation with her performance as Lilo in Wolfgang Becker's Life is All You Get (Das Leben ist eine Baustelle). In 1997, she received the German Film Award for Best Actress in a Supporting Role for her performance as a shy waitress in Helmut Dietl's Rossini – oder die mörderische Frage, wer mit wem schlief (de). By the end of the 1990s, Gedeck had established herself as "one of the most prolific character actresses in Germany" with ambitious feature films such as Jew-Boy Levi (Viehjud Levi) and television dramas like Dominik Graf's Deine besten Jahre. She garnered awards and nominations throughout this period of her career.

Gedeck's international breakthrough came with her performance in Sandra Nettelbeck's Mostly Martha (Bella Martha). In the film, she plays a workaholic chef who is forced to adjust to major changes in her personal and professional life that are beyond her control. The film won the Créteil International Women's Film Festival Grand Prix Award, and the Goya Award for Best European Film in 2002. It also received a German Film Award Nomination for Outstanding Feature Film. For her performance, Gedeck received a European Film Award Nomination for Best Actress (2002), the German Film Award for Outstanding Individual Achievement for Actress (2002), and the German Film Critics Association Award for Best Actress (2003).

In 2006 Gedeck appeared in five major films: The Elementary Particles (2006) as Christiane, The Lives of Others (2006) as Christa-Maria Sieland, The Perfect Friend (2006) as Marlène, Summer '04 (2006) as Miriam Franz, and Robert De Niro's The Good Shepherd (2006) as Hanna Schiller, starring opposite Matt Damon and John Turturro. The Lives of Others won the Academy Award for Best Foreign Language Film.

In 2008 Gedeck played the role of Ulrike Meinhof in The Baader Meinhof Complex. In 2010, Gedeck, who is affiliated with the Green Party, served as an elector in the Federal Assembly to elect the new President of Germany. That year, she appeared in Jew Suss: Rise and Fall and Agnosía.

In 2012 she appeared in The Wall and The Door, and in 2013, she appeared in The Nun and Night Train to Lisbon. Gedeck resides in Berlin with her partner, Swiss Director Markus Imboden. In 2013 she was named as a member of the jury at the 70th Venice International Film Festival.