Born in Merano, South Tyrol, the son of a butcher, Steiner studied engineering without completing his degree. He moved to Belgium and began his motorsport career as a mechanic for Mazda Rally Team Europe from 1986 to 1988. From January 1989 to 1990, he was assistant team manager for Top Run Srl, then served as head of reconnaissance and later technical manager at Jolly Club from 1991 to 1996.
In 1997 Steiner managed Prodrive's Allstar Rally team, winning the European Rally Championship with Krzysztof Hołowczyc. In 1998 M-Sport recruited him as project manager; he was promoted to director of engineering in 2000, working alongside Colin McRae and Carlos Sainz at the Ford World Rally Team. The team achieved consecutive runner-up finishes in the 2000 and 2001 seasons.
Steiner switched to Formula One in 2001 when Niki Lauda headhunted him to become managing director of Jaguar Racing, Ford's official Formula One works team, at Milton Keynes. Director of strategy John Allison handled administrative tasks alongside Steiner's engineering responsibilities. Steiner reorganised the team and reduced costs, but Jaguar underperformed in the 2002 season: lead driver Eddie Irvine claimed only eight championship points while teammate Pedro de la Rosa failed to score. Ford dismissed Niki Lauda on 26 November and made 70 team members redundant. On 5 December, Jaguar announced Steiner had been replaced by project manager David Pitchforth. A spokesman stated: "he has relinquished his responsibilities as MD but has done nothing wrong." Steiner declined an alternative role offered by the new management and spent the 2003 season on garden leave before becoming technical director at Opel Performance Center in November of that year.
After Red Bull purchased Jaguar Racing in November 2004, Steiner was invited to join Red Bull Racing. His appointment as technical operations director was confirmed on 13 January 2005. He and team principal Christian Horner jointly led the team to improved results in the 2005 season. When Red Bull recruited Adrian Newey from McLaren, team owner Dietrich Mateschitz approached Steiner to help establish a NASCAR team in the United States. Steiner moved to Mooresville, North Carolina, serving as technical director for Team Red Bull's NASCAR programme from 1 April 2006 to April 2008.
Steiner remained in Mooresville after leaving Red Bull, founding the manufacturing company Fibreworks Composites in January 2009. He wrote a business plan for a new Formula One entry during the financial crisis of the late 2000s, seeking a financial backer. He met Joe Custer and Gene Haas of Stewart–Haas Racing at a steakhouse and proposed they enter Formula One by ordering a customer car from an established constructor. Delays in securing approval led them to apply as a privateer team. Steiner has credited support from figures including Niki Lauda, Stefano Domenicali, Jean Todt, and Charlie Whiting as crucial to convincing Formula One leadership, including Bernie Ecclestone, to approve the entry. Motorsport publication Autosport described Steiner as "the prime 'doer'" of the project. He recruited core staff, interviewed every team member, and developed partnerships with outsourcers Dallara and Ferrari. On 14 April 2014 he was officially announced team principal of Haas F1 Team.
With their entry in the 2016 season, Haas became the first American constructor to compete in Formula One in 30 years. Romain Grosjean finished sixth at the 2016 Australian Grand Prix, scoring eight points — the first points finish for an American entry and the first for any constructor since Toyota Racing in 2002 on a debut race. Haas completed the 2016 season eighth in the Constructors' Championship with 29 points, all scored by Grosjean.
Steiner became widely known for his forthright personality through appearances on the Netflix series Formula 1: Drive to Survive. In 2023 he released the book Surviving to Drive: A year inside Formula 1. In January 2024, Haas chose not to renew his contract for the 2024 season; he was replaced by Ayao Komatsu, the team's former trackside engineering director.
In May 2024, Steiner sued Haas for non-payment of commissions owed over several years and for continued use of his name and image without authorisation. Days later, Haas Automation, the parent company of Haas F1 Team, counter-sued Steiner and his publisher Ten Speed Press for trademark infringements in Surviving to Drive. In September 2024 Haas Automation's lawsuit was dismissed. In October 2024 Steiner released a second book, Unfiltered: My Incredible Decade in Formula 1, and undertook a UK live show tour between November 2024 and June 2025 to promote it.
In late February 2024 Steiner signed a contract with RTL, a German television channel broadcasting Formula One in Germany, as a specialist commentator, attending multiple Grands Prix during the 2024 season. He also began a role as race ambassador for the Miami Grand Prix in April 2024. In September 2025, Steiner was named head of the consortium that acquired the Red Bull KTM Tech3 MotoGP team.
Steiner holds Italian and American passports. A native of South Tyrol, he speaks German, Italian, and English. He lives in Mooresville, North Carolina, with his wife Gertraud and daughter.
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