After starting out in rock bands (Puma, with Gard Nilssen and Øystein Moen, and Monolithic, with Motorspycho member Kenneth Kapstad), Westerhus broadened his stylistic scope and joined the large Norwegian ensemble Jaga Jazzist. Later on, Nils Petter Molvær invited Westerhus to perform on his album Baboon Moon. Westerhus made his international breakthrough by collaborating with Norwegian singer Sidsel Endresen: a pair of excellent improvisers, understanding each other perfectly. The duo was awarded the Spellemannprisen in 2012 for their album Didymoi Dreams.
Nowadays, solo projects dominate Westerhus’s artistic scope. He has released four albums to date: Galore, Amputation, Pitch Black Star Spangled, and The Matriarch And The Wrong Kind Of Flowers.
Westerhus and his family live near Trondheim on a remote farm.