Altemeyer has long been involved in social justice and environmental issues in the Winnipeg area. He was responsible for bringing a recycling program to the University of Manitoba, and was one of the founders of the Global Change Game (an internationally-respected educational program) while still a student. Altemeyer served a two-year term on the Council of Canadians, and has taken part in a variety of activities in the fair trade/anti-globalization movement. In 1998, he organized an anti-globalization study group known as Beyond McWorld.
Altemeyer has also been involved in the Wolseley Neighbourhood Advisory Committee, which is involved in over two dozen local capital improvement projects. Prior to the 2003 provincial election, he served as an assistant to NDP Cabinet Minister Tim Sale.