Moskowitz was born in the Romanian Jewish village of Frumușica in 1928. There were six members of the Moskowitz family, including a father, mother, three sons and one daughter. The father of Reuven, Shlomo Moskowitz, was a cantor and a violinist. When Reuven was a child, he would accompany his father while singing in the synagogue. He already played the violin at the age of five, and in his adulthood, he was introduced to the harmonica, which he bought from a Palestinian boy in Ramallah after the Six Day War. It was from that day on that the harmonica became an integral part of his life, accompanying every activity of his, family, social or political. In the Moskowitz family, there have been generations of musicians who have not received conventional musical training, but who have perfected their musical skills through improvisation and absolute hearing. Throughout world wars and hardships of life, music was the language of their hearts and spirits.

Upon turning eighteen, Reuven immigrated to Israel, as part of the Youth Immigration program, and lived in Kibbutz Misgav-Am, where he met his future wife, Varda. From the kibbutz, they moved to Haifa, where they had their first child, Samdar. In the beginning, Reuven worked as a dock worker until the family moved to Jerusalem, where he pursued two degrees, one in history and one in biblical studies, at the Hebrew University.

In Jerusalem, Varda and Reuven Moskowitz welcomed their second child, Shlomi (Shlomo) Moskowitz. Following graduation, Reuven became a teacher at De Shalit High School in Rehovot.

It was in the wake of the Six Day War of 1967 that Reuven became the secretary of the Movement for Peace and Security – a political movement established in July 1968. It was a Non-partisan political movement working primarily against the annexation of the West Bank and for Palestinian rights to self-determination and sovereignty.

In 1972, Reuven was one of the founders of the village Neve Shalom – Wahat al Salam, where Jews and Palestinians still live in partnership today. In addition to his intense political activity, Reuven also worked as a tour guide for a number of years in Israel, Romania, and Germany. As a guide, he led mixed groups of Jewish-Israelis, Germans, Romanians and Palestinians. In the early nineties, Reuven and his wife Varda were involved in several joint projects. Among them was a project for residents of the Romanian village of Sancho Florești, conducted in cooperation with the German government. As part of the project, young guides from Germany assisted in children's summer camps in the village. For the children, it was a unique and memorable experience. Additionally, Reuven and Varda organized sightseeing trips for women who had never left their village before.

While working in Romania, they established the Romania-Germany Friends Committee, which has helped raise donations for the benefit of Romanian villagers for many years.

As part of his research into the historical processes preceding the Jewish-Palestinian conflict, Reuven visited Germany and experienced a country and a people that held themselves accountable for their difficult past. Through seminars, lectures, and visits to various schools in Germany, he explained Germany's part in the historical responsibility for the Jewish-Palestinian conflict. Together with groups from the peace movements, Reuven has organized aid to the West Bank and Gaza since the outbreak of the Second Intifada, and has given lectures around the world regarding the Middle East conflict. It was Reuven's life's mission to promote reconciliation among the Germans and the Israelis, as well as between the Jews and the Palestinians.

Throughout his book The Long Road to Peace: Germany – Israel – Palestine: Chapters from the Life of a Peace Adventurer, he explained the tragic entanglement of these three nations and Germany's role in this matter. Reuven urged Europe, particularly Germany, to intervene in the resolution of the Israel-Palestine conflict. Reuven stated during one of his lectures at the Anne Frank Comprehensive School, "Without outside assistance, we will not achieve peace".

In recognition of his many accomplishments, he was awarded the Aachen Peace Prize in 2003 together with Palestinian activist Nabila Espagnoli, an educator, feminist, and candidate for the Knesset on behalf of the Hadash party. “The prize was accorded them for raising hope along the way to peace and conciliation between Jews and Palestinians”, said chairman Gerhard Dieffenbach of The Aachen Peace Prize committee. A German organization called "Religious for Peace" was also awarded the prize in the same year.

Reuven was awarded the Har-Zion Prize in 2001, alongside Kifaya Jadah and Emil Shoufany, by the Har-Zion Foundation, which is based at the Institute for Jewish-Christian Research (IJCF) at the University of Lucerne in Switzerland. As a result of the efforts of a German priest named Wilhelm Salberg – the son of a Jewish father and a Christian mother – the foundation was founded in 1986. Mount Zion Awards are presented to those of Jewish, Muslim or Christian faith who have contributed significantly to the Jewish-Christian dialogue or to the promotion of dialogue between the three Abrahamic religions in Israel.

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On August 4, 2017, Reuven Moskowitz passed away at the age of eighty-nine. He still aspired, up to the very end of his life, to establish a peace center in Berlin that would be able to carry on its broad-based work for many years to come.