Muller earned a master's degree in business economics from Erasmus University Rotterdam.

[2] Muller started his career with KLM Cargo, from 1988 to 1997.

[1] In 2013, Muller joined Delhaize as president and CEO.

[1] Muller was CEO of Delhaize until Ahold bought the company for Euro 9.3 billion in 2015, when he became deputy CEO of the combined company.

[3] Muller succeeded Dick Boer when he retired as CEO of Ahold Delhaize on 1 July 2018.