As early as 1934, Segerstedt-Wiberg helped organise a committee to aid Jewish refugee children who arrived in Sweden on their own, establishing an orphanage on Viktoriagatan in Göteborg. After the war she continued to work with refugees, chaired the Swedish section of the Women's International League for Peace and Freedom, as well as UNA-Sweden, and was a member of the Swedish UNICEF National Committee.
Segerestedt-Wiberg also worked as an editor (1949-1953), and publisher (1968-1973), for the magazine Världshorisont, Göteborgs-Tidningen (a Gothenburg tabloid) between 1949 and 1955, and finally Göteborgs-Posten — where she served as assistant editor between 1969 and 1976. A indefatigable activist, Segerstedt-Wiberg was Sweden's first female editorialist, and authored some fifteen books.
As a representative for Folkpartiet (Liberal People's Party), Segerstedt-Wiberg was elected member of parliament between 1958 and 1970, leaving the party in 1999 following its decision to endorse Swedish NATO membership. Throughout her life, she remained a strident, vocal challenger of the xenophobia far too prevalent in Swedish society.