Felicia Langer arrived in Israel from Poland in 1950 with her husband, who was a survivor of the Nazi concentration camps. After studying law she had her own legal practice in Tel Aviv from the mid-1960s.

After the Six-day War of 1967, in which Israel seized all the land from Jerusalem to the west bank of the River Jordan, Langer was shocked by the Israeli regime in the occupied territories and began to defend Palestinian victims of oppression and injustice. For 22 years she single-mindedly fought a system of Israeli lawlessness, administered in particular through military courts. Her accounts of the treatment of her clients by the Israeli military make chilling reading: systematic and widespread torture, sometimes culminating in death; confessions extracted under duress; routine violation of the international laws against deportation and collective punishments, such as demolition of the homes of those who 'confessed' to crimes, thereby rendering their whole families homeless.

Whereas Jewish settlers obtained grants of land at the expense of Arabs, Palestinian families were denied reunification and sometimes even any sort of nationality. As the only solution to this situation, Langer called for an end to the occupation and an independent Palestinian state on the West Bank.

For this work Langer suffered enormous abuse and hardships at the hands of her fellow Israelis and lived under the permanent threat of violence. Her secretary said that Langer could seldom walk down the street without suffering some form of verbal or physical abuse. A fellow lawyer has said that it is rare for an advocate to endure the harsh conditions of the military courts for more than three years: Langer's more than two decades was unique. In addition to her legal work, Langer wrote three books during her time in Israel: With My Own Eyes (1975), These Are My Brothers (1979) and An Age of Stone (1987). Since then, she has published several more books. She also undertook numerous speaking tours in Europe and the USA, exposing human rights violations in her country and mobilising support for the Palestinians and the Israeli peace movement.

In 1990, Langer moved to Tübingen in Germany to take up a university post. On leaving Israel she told the Washington Post in an interview: "I decided I could not be a fig-leaf for this system any more. I want my quitting to be a sort of demonstration and expression of my despair and disgust with the system...because, for the Palestinians, unfortunately we cannot obtain justice."

Since moving to Tübingen, Felicia Langer speaks at public meetings, all over Germany, Switzerland and Austria, trying to mobilize solidarity with the Palestinian people and the Israeli peace forces. In 2009, she received Germany's Federal Cross of Merit, 1st Class.