Pei was born in 1989 in China, shortly after which he and his parents moved to the United States. A couple of years later, his family moved to Sweden, where Pei spent most of his childhood. Pei pursued his Bachelor degree at the Stockholm School of Economics, but dropped out in 2011 to work full-time in the smartphone industry.
Carl Pei studied BSc at Stockholm School of Economics between 2008 - 2011, before dropping out. He then worked as International Markets Manager at OPPO Electronics from November 2012 - December 2013, before leaving to co-found OnePlus.
Pei joined Nokia in 2010, and worked at the company for three months. After Nokia, the fan website Pei had created about Meizu had caught the attention of the company's Hong Kong branch, where Pei started working in Meizu's marketing team in 2011. A year later, Pei joined Oppo as its international markets manager, where he worked directly under Pete Lau.
Pei co-founded OnePlus with Pete Lau in December 2013. The first OnePlus device, the OnePlus One, sold close to a million units in 2014, despite a sales target of only 50,000, according to Pei. OnePlus launched the OnePlus 2 in July 2015 through a virtual reality video on YouTube, presented by Pei. OnePlus claimed its video was the first product launch in virtual reality, and the video has been viewed 289,000 times as of October 2017. The OnePlus 3 was unveiled in June 2016, and Pei claimed it was the company's most popular smartphone, according to the Net Promoter Score tracked by OnePlus. OnePlus released the OnePlus 3T in November 2016. Pei said the reason for the upgrade from the OnePlus 3 to the OnePlus 3T was because the company wanted to improve both the software and hardware. The OnePlus 5 was released in June 2017, and Pei claimed it to be the fastest-selling OnePlus device to date. The OnePlus 5T was released in November 2017 which was the first phone with 18:9 display along with some changes from OnePlus 5.
In July 2015, Pei was interviewed by The Wall Street Journal about how OnePlus was created. Pei stated:
One of the reasons why we started this company was we looked at all the Android phones on the market and there wasn't one phone that was good enough for us ourselves to use.
In June 2015, Pei was interviewed by Forbes about the globalization of OnePlus. Pei stated:
OnePlus wasn’t meant to become a global company at the beginning. The main focus was taking on the China market. When we started the company, we built a management team with a lot of experience in the China market. But for the global markets team, we are a bunch of young people without a lot of experience. It was just like an experiment, “Hey, do the global markets and see what happens. Do whatever you want.” We call our group “a Shenzhen within our company”, or a start-up within a bigger company.
In October 2014, Pei was interviewed by The New York Times about the growth and market approach of OnePlus. Pei stated:
We don’t really think of ourselves as a Chinese start-up. Very soon our sales outside of China will surpass sales in China.