David Ross, who helped set up the firm with chief executive Charles Dunstone 16 years’ ago, cashed in on a recent surge in the price of the stock by selling six million shares.
Mr Dunstone pocketed roughly the same amount when he made his first sale since the group floated in 2000. Both said they had no current intention to sell any further shares.
Deputy chairman Mr Ross helped set up the business in 1989 after joining from accountancy firm Arthur Andersen.
He stepped down from his role of chief operating officer at the company’s annual meeting in 2003 to take up his current post, which leaves him focused more closely on the strategic development of the group.
No reason was given for the sale, which was processed on Friday at 258c a share and which left Mr Ross with 22% of the company.
Carphone Warehouse, which has around 1,085 shops in 12 countries, has seen its shares rise by almost a fifth in the past month.