Muller studied Law at Leiden University. After graduating in 1984, he became a lawyer for the Amsterdam office of law firm Baker & McKenzie. In 1989, he joined the management team of offshore company Heerema in Leiden. A management buyout made him part owner of salvage and towing company Wijsmuller in IJmuiden. From 1992 onwards, Muller led several companies, such as Emergo Mode Groep (Emergo Fashion Group), which would be launched on the Amsterdam Stock Exchange as McGregor Fashion Group.
Muller and Maarten de Bruijn founded Dutch car company Spyker Cars in 2000. Muller was the CEO of the company until May 16, 2007, when he was succeeded by Michiel Mol. Muller continued to work for the company as chief designer.