Boris Dittrich was the first openly gay member of Dutch parliament who focused on LGBT rights. In 1994 he proposed to introduce marriage equality. Dittrich and two colleagues embarked on a long campaign. In spite of fierce opposition from religious groups, the Netherlands became the first country in the world to introduce marriage equality.

Boris was member of the Dutch House of Representatives from 1994–2006 and since 2019 member of the Dutch Senate. Between 2007-2018 he was advocacy director in the LGBT rights program with Human Rights Watch.

In early 2007 Dittrich became Advocacy Director of the Lesbian, Gay, Bisexual & Transgender (LGBT) Rights Program at Human Rights Watch in the Headquarters of the non-governmental organisation in New York City.

Dittrich worked on different levels to achieve non-discrimination and equal rights for LGBT people. In New York he co-organised yearly events at the United Nations to celebrate International Human Rights Day on December 10. In 2007 he chaired the event that introduced the Yogyakarta Principles to the UN in New York. The 2008 event introduced a joint statement by 66 countries to denounce violence and discrimination against people because of their sexual orientation or gender identity.

Mid 2013 Dittrich moved from New York to Berlin, Germany where he continued to work as global advocacy director of the LGBT Rights Program at Human Rights Watch until October 2018.

In 2019 Dittrich was elected as senator in the Dutch Senate for his political party D66.