In 1979, Daniel Brélaz became the first green representative elected to sit in a national parliament.

On 25 November 2001, he became the trustee responsible for finance, and was re-elected in the first round of Vaud elections on 12 March 2006.

He resigned his seat on the Grand Council of Vaud but remained a trustee in Lausanne, and was criticized for maintaining this dual mandate.

On 13 March 2011, he was re-elected in the first round of the Lausanne municipal elections with 11,503 votes in his favour.

Brélaz is vice-president of the Administrative Council for Public Transportation in the Region of Lausanne.