Brawn was born in Ashton-under-Lyne, Lancashire, England. He developed an early interest in engineering, often visiting Belle Vue Stadium to watch motor racing. His family moved south when his father took a job near Reading, Berkshire, and he attended Reading School. In 1971, he began as a mechanical craft apprentice at the United Kingdom Atomic Energy Authority’s Atomic Energy Research Establishment in Harwell, Oxfordshire, qualifying as an instrument mechanic. He continued his education with an HNC in Mechanical Engineering, funded by Harwell. While living in Reading, he responded to an advertisement from Frank Williams Grand Prix and was interviewed by Patrick Head, securing a position as a milling machinist.
Brawn’s career in motorsport began in 1976 with March Engineering as a milling machine operator, progressing to a mechanic role within their Formula 3 racing team. In 1978, he joined Frank Williams as a machinist for the newly formed Williams team, moving into R&D with Frank Dernie and as an aerodynamicist.
He joined the Haas Lola team in 1985, contributing to the design of the Lola THL1 and THL2 cars. He then moved to Arrows in 1986, designing the Megatron-powered Arrows A10 and A10B for the 1987 and 1988 seasons, followed by the Ford V8-powered Arrows A11 in 1989. Later in 1989, Brawn became lead designer on the Jaguar XJR-14 at Jaguar Sportscar racing, which won the 1991 World Sportscar Championship.
Brawn returned to Formula One in late 1991 as technical director of Benetton, helping Michael Schumacher win World Drivers' Championships in 1994 and 1995, and the World Constructors' Championship in 1995. He also persuaded Frank Dernie to join to help with car development and improve the team organisation.
Following Schumacher to Ferrari in late 1996, Brawn played a key role in the team’s resurgence. As technical director, he helped Ferrari win the Constructors' Championship in 1999, initiating a streak of six consecutive titles. Schumacher secured five consecutive drivers' titles under Brawn’s guidance from 2000 to 2004. Many label Brawn as a vital member of the Ferrari "dream team" alongside Schumacher, team principal Jean Todt, and chief designer Rory Byrne. He received an honorary degree of Doctor of Engineering (DEng) from Brunel University in 2006 for his services to motorsport.
Towards the end of 2007, Brawn was announced as the new team principal of Honda. With Honda’s withdrawal from Formula One in late 2008, Brawn acquired the team in March 2009, renaming it Brawn GP. The 2009 season saw Brawn GP achieve remarkable success. Jenson Button qualified on pole position at the Australian Grand Prix, finishing first alongside teammate Rubens Barrichello. Throughout the season, Button won six races and Barrichello won two, with the team consistently achieving podium finishes. Brawn GP secured both the 2009 Constructors' Championship and the Drivers' Championship with Button at the Brazilian Grand Prix.
In November 2009, Daimler AG bought Brawn GP, forming Mercedes. Brawn remained as team principal and co-owner with Nick Fry. The team won their first race on 15 April 2012, when Rosberg won the Chinese Grand Prix.
Brawn returned to Formula One in 2017 as managing director, Motor Sports, and technical director for the Formula One Group. He oversaw significant technical and sporting regulation changes aimed at improving the competition and spectacle of the sport. Following the 2022 season, he retired from Formula One. He received a second honorary doctorate from Heriot-Watt University on 18 November 2011 and was appointed Officer of the Order of the British Empire (OBE) in the 2010 New Year Honours for services to motorsport.
Brawn released Total Competition: Lessons in strategy from Formula One, co-authored with Adam Parr, in 2016. He became a patron of Hope for Tomorrow, a charity providing mobile cancer care units. In 2010, he established the Brawn Lifeboat Challenge, raising £360,000 for a new lifeboat for the River Thames.