The honour, announced in June, was given in a ceremony at Buckingham Palace on Tuesday.
Robertson established ASOS in 2000 as AsSeenOnScreen, a fashion portal that promised shoppers the goods they needed to get the look of style stars.
Ten years and one web-friendly name abbreviation later, ASOS is on track to achieve £1bn in sales by 2015.
Celia Birtwell was awarded a CBE in the same group.
I have always loved designing, never seeing it as work, a means to an end, or a chore, she told us over the summer. It is what keeps me energised and challenged on a daily basis and so to be awarded a CBE for something that is already a pleasure for me is simply wonderful.More