In 1998, Winterbottom visited America on a family holiday and heard about a major karting event taking place close by – so a last-minute decision was made to rent a kart locally and compete. Winterbottom then won the Knoxville State Championship title race. In 1999 he competed in Japan at the Suzuka Champions Kart race on invitation.

In 2001 Winterbottom was crowned as Australian Formula A Kart Champion (Rotax 125cc Class).

In 2001, Winterbottom made his Formula Ford debut in the Victorian Formula Ford Championship. Winterbottom raced to runner-up honours after winning four races out of six rounds, missing one round due to karting commitments. He won the Ford Kart Stars Scholarship Championship, gaining a Ford-supported drive in the 2002 Australian Formula Ford Championship.

He finished second in the 2002 Australian Formula Ford Championship with two round victories, five race wins and two pole positions. The championship was won by Winterbottom’s future V8 Supercars rival Jamie Whincup. He was presented with 2002 Avon Formula Ford Rookie of the Year Award.

In 2003, Winterbottom became the Konica V8 Supercar Series champion in his debut season. Winterbottom raced with Ford team Stone Brothers Racing (SBR) to five round victories and six pole positions in an almost perfect season. Two of Winterbottom’s race victories were gained from rear-of-field reverse grid starts. He missed out on making a clean sweep of the series due to an engine failure in the fifth round at Phillip Island.

Winterbottom joined Ford V8 Supercar team Larkham Motor Sport (LMS) and competed in the 2004 and 2005 V8 Supercar championships. Highlights of his debut season included a fifth-place finish at Bathurst and sixth-place result at Sandown in 2004. Winterbottom’s best qualifying result was fifth at the Darwin round in 2005. The lowlight was at the V8 Supercars China Round in which Winterbottom avoided injury after a loose drain cover penetrated the chassis floor and damaged the driver’s seat.

In 2010, Winterbottom was a distant yet mathematical chance of winning the championship title heading into the final round, the Sydney 500. However a crash, which ironically also involved fellow contenders Whincup and James Courtney, in wet conditions in the Saturday race ruled Winterbottom out of the title race.

In 2011, Winterbottom finished a distant third to the Triple Eight Race Engineering cars. He scored two wins, at the Gold Coast 600 with international co-driver Richard Lyons and in the final race of the year at the Sydney 500.

Winterbottom was used as the voice of the character ‘Frosty’ in the Australian Release of the 2011 Pixar film Cars 2. He also appeared as a contestant on Season 3 of the Seven Network’s celebrity series Australia’s Greatest Athlete in 2011.

In 2013, Winterbottom won the Bathurst 1000 alongside ex-teammate Steven Richards on 13 October. However, due to a poor start to the championship, Winterbottom was only able to finish fourth in the championship, with three race wins. Teammate Will Davison finished narrowly ahead in third, aiding FPR’s rise in the Teams’ Championship to finish second for the first time.

In 2014 Winterbottom started the season very well, leading the championship by 161 points after the 2014 Skycity Triple Crown in June. Despite high hopes of claiming his first title, Winterbottom’s campaign ultimately crumbled against the Triple Eight juggernaut. He did not win another race after the Darwin round. At the 2014 Supercheap Auto Bathurst 1000, Winterbottom was a chance of going back-to-back late in the race, until an incident with an attacking Craig Lowndes resulted in him dropping back, and eventually recovering to take a fifth-place finish. As in 2012, going into the final round in Sydney, Winterbottom was second with Whincup in first and out of reach. However, Shane van Gisbergen won the Sunday race to demote Winterbottom to third in the standings.

In 2014 and 2015, Winterbottom appeared in the season-opening two-driver round of the Stock Car Brasil championship, for Voxx Racing. In 2014, he drove alongside Sérgio Jimenez to fourth at the Autódromo José Carlos Pace whilst in 2015 he finished second with Marcos Gomes at the Autódromo Internacional Ayrton Senna. Just like Winterbottom, Gomes went on to win his respective championship title in 2015. Winterbottom returned to Brazil in 2018, finishing eleventh at the Autódromo José Carlos Pace driving with Átila Abreu, despite starting from the rear of the grid.

In 2015, Prodrive Racing Australia (the new name for Ford Performance Racing, due to reduced support from Ford) debuted the Ford FG X Falcon, and it brought considerable success almost immediately, with Winterbottom taking four wins out of four races at the non-championship V8 Supercars Challenge event at the Australian Grand Prix. Winterbottom then achieved eight race wins in the middle part of the championship year, including a clean-sweep of the 2015 Castrol Edge Townsville 400. This resulted in Winterbottom taking a large championship lead into the endurance races. Driving with Steve Owen, Winterbottom then went on to increase his lead with his ninth win of the year at the 2015 Wilson Security Sandown 500, before finishing second at the 2015 Supercheap Auto Bathurst 1000. Despite not winning a race after Sandown, Winterbottom held on to secure his first championship title in a showdown against Craig Lowndes at the final round, the Sydney 500.

2017 saw Winterbottom complete a winless year for the first time since moving to Ford Performance Racing in 2006. Highlights included podiums at the Phillip Island 500, Townsville 400 and Auckland SuperSprint, while the lowlight was crashing out of the Bathurst 1000 on the penultimate lap while battling for fifth place. Winterbottom secured sixth in the championship for the second consecutive year, albeit only after Craig Lowndes’ late retirement at the season-ending Newcastle 500.

In 2018, Prodrive Racing Australia was again renamed, to Tickford Racing, and Winterbottom began the year with a top five Saturday result at the Adelaide 500 before a pit lane penalty dropped him down the field in the Sunday race. His fortunes did not improve, with Tickford Racing enduring a difficult start to the season until Winterbottom scored both his and Tickford Racing’s first race podium of the year at the fifth event at Barbagallo. It was confirmed on 1 November that Winterbottom would leave Tickford Racing at the end of the 2018 season, after 13 years with the team. Despite a difficult final season with the team, in which he finished only 12th in the championship, Winterbottom left the team with a record of 412 race starts, 38 wins, 35 poles and 117 podiums.

Winterbottom announced ahead of the 2018 Newcastle 500 that he would be moving to Team 18 in 2019, the first time he will have driven a Holden in his career.