Rebecca Harms co-founded the citizens' initiative against the Gorleben nuclear waste storage facility in 1977. She first visited the Chernobyl restricted area in 1988. From 1994 to 2004, she was a Member of the Lower Saxony Landtag and from 2004 to 2019, she was a Member of the European Parliament for the Greens. From 2009 to 2016, she was co-chair of the Greens/EFA Group in the European Parliament.