Dixons Carphone said Shop Direct's Alex Baldock was joining as its chief executive in an announcement late on Friday, after it emerged that current boss Sebastian James had resigned from the role to run Boots.
It is thought the changes in leadership were supposed to be announced together at a later date.
However, a Sky News report on Friday evening forced Dixons Carphone to rush out a statement, amid signs the departure could shake investors ahead of Dixons Carphone's Christmas trading results on Tuesday.
Mr James is joining Walgreens Boots Alliance later this year, as its senior vice president, and president and managing director of pharmacist Boots.
News that Mr James is stepping down from a role he has held at the electricals retailer since 2014 may not prove a huge shock to the market, after he was linked to the top job at ITV this summer.
However, the timing of his departure – less than two weeks after Marks & Spencer poached Dixons Carphone's finance director Humphrey Singer – appears to signal big change at Dixons Carphone.
Both Mr James and Mr Singer were part of the so-called "Dixons mafia" group of executives who have enjoyed success during their careers at the business.
However, a shake-up of the executive team could be welcomed by some investors, who last summer told the board to step up succession planning, after profits at Dixons Carphone plunged.
Last month the retailer announced an overhaul of its mobile phone business, and sources have suggested it also needs to restructure its vast estate of shops.
Mr Baldock, who announced he was leaving Shop Direct in October and will step down at the end of this month, will be taking the reins at Dixons Carphone. During his time at the online retailer, he managed to successfully steer Shop Direct from a catalogue retailer to a profitable digital business.
The group posted record sales last October, thanks to a jump in mobile phone shoppers, and more recently it has been focused on the use of artificial intelligence in examining customers' buying patterns.
Shop Direct is owned by Sir David and Sir Frederick Barclay, who are the proprietors of Telegraph Media Group.