As both brands seek to adapt to "current challenges" facing the high street, O2 has joined forces with four Next stores.
In a new trial, shoppers will be able to browse and buy O2 products and services alongside Next's clothing and homeware offer.
The two brands are hoping this will appeal to consumers seeking convenience.
One of the stores taking part in the trial, is the Next branch at Giltbrook Retail Park.
The trial will also be launching in Next's Warrington Gemini, Southampton Hedge End and Swindon Orbital.
The first stores, in Warrington and Southampton, open on Friday, with the second two to follow next month.
O2's Shop-In-Shop will be prominently positioned on either the ground or first floor in each Next store, with the aim of attracting maximum footfall as customers browse.
Each store will be approximately 650 square feet in size, offering a range of products and services in line with those of traditional O2 stores.
O2 sales director Gareth Turpin said: "We are delighted to be working with Next on the launch of our Shop-In-Shop trial.
"The current challenges facing the high street are never far from the headlines, but we are committed to driving innovation within our retail business by embracing flexibility.
"We look forward to hearing their feedback on the trial and are excited to roll this out more widely in the coming months."
Next reported a 2.7% rise in pre-tax profits to £319.6 million for the six months to July as online sales growth continued to offset high street woes.
The group reported a 4.9% fall in like-for-like sales across its 499 high street shops, but online sales jumped 12.6%, leaving overall full-price brand sales up 4.3%.
O2 revealed in July that revenues in the UK jumped 5.1% in the year to £2.98 billion with underlying profits, the company's preferred measure, up 6.4% to £919 million in the six months to June 30.
O2 has more than 450 retail stores across the UK.
