Katja Weilandt was born in Berlin in 1982. From 2000 until 2004, she studied acting at the Staatliche Hochschule für Musik und Darstellende Kunst in Stuttgart. Nicolette Krebitz discovered her, and did cast her in her 2001 directorial debut "Jeans" (2001). The same year, she also appeared in Krebitz' short "Mon Chérie", which was part of the "99 Euro Films" project.

Following her graduation, Weilandt played supporting roles in the TV production "Saniyes Lust" (2004) and Irene von Alberti's contribution to the compilation film "Stadt als Beute" ("Berlin Stories", 2005). She went on to be a cast member on the TV miniseries "They Call Us Candygirls" (2008), guest-starred in the "Polizeiruf 110" episode "Blutige Straße" (2011), and also appeared in the theatrical release "Weil ich schöner bin" ("Cause I have the Looks", 2012). Frequently working with director Julian Radlmaier, she had parts in his films "Ein Gespenst geht um in Europa" (2012), "Ein proletarisches Wintermärchen" (2014) and "Selbstkritik eines bürgerlichen Hundes" ("Self-criticism of a Bourgeois Dog", 2016). Züli Aladag cast her in "Der Kriminalist - Tod gegen Liebe" (2009), "Der Kriminalist -Tod eines Begleiters" and in "Marthaler - Die Sterntalerverschwörung" (2017). Katja Weilandt was one oft he leads in Irene von Alberti's feature film "Der lange Sommer der Theorie" ("The Long Summer of Theory"), which premiered at the 2017 Munich Film Festival.