In 2006 he raced in the NASCAR Craftsman Truck Series, piloting the #20 Team Australia/Aussie Vineyards Ford for Team Australia. He moved up to the 2007 NASCAR Busch Series, driving the #59 Kingsford Charcoal Ford Fusion for Wood Brothers/JTG Racing.
He moved into Formula Ford in 1996. The Ambrose family have a rich history in this formula as Marcos' father Ross Ambrose, along with Ralph Firman Sr, co-founded Formula Ford chassis builder Van Diemen. Ambrose finished second in the Australian Formula Ford championship in 1997.
In 1998 Ambrose moved to Europe in a bid to reach Formula 1, competing in British Formula Ford in 1998 and 1999. In 1999 he won the European Formula Ford Championship. In 2000 he began the season racing in the French Formula 3 Championship, before switching mid-season to the British Formula 3 Championship.
At the end of 2000 Ambrose did not have the budget to continue in racing in Europe, and returned to Australia. In October 2000 he was invited to compete in a Young Guns invitational race held at the Gold Coast Indy 300. Ambrose won against a host of young drivers in Honda road cars.
He also represented Australia in the 1996 EFDA Nations Cup at Donington Park in England.
For 2001 Ambrose was signed by Stone Brothers Racing to drive the Pirtek Racing Ford Falcon. Ambrose stunned the V8 Supercar world when he qualified on pole for his first ever V8 Supercar race, supporting the Australian Grand Prix (a non-championship event before the championship season). Qualified on pole again in round three at Eastern Creek Raceway, round 9 at Queensland Raceway and round 11, the Bathurst 1000 at Mount Panorama Circuit.
Ambrose went on to finish eighth in the championship, winning the Rookie of the Year award. He won the fourth round of the season, at Hidden Valley Raceway in Darwin, although he did not win any of the three races in the round.
The 2002 season saw Ambrose start the season snaring the pole position at Phillip Island before recording his debut race win in the first race. He eventually finished third in the V8 Supercar Championship.
With a new BA Falcon, Ambrose gave the Ford team a great start to the 2003 season with victory in the first race of the Clipsal 500 in Adelaide. He followed this fantastic start with a third career win at Eastern Creek Raceway where he led Ford home to a memorable 1-2-3 at the Sydney track. This was Ford's first clean sweep of the podium since Eastern Creek 1997 and Ambrose’s first win for the season. After 13 rounds in the 2003 V8 Supercar Series, Ambrose was presented with the driver’s series trophy, 102 points clear of second place.
In 2004 Ambrose claimed three pole positions and five round wins and went into the final round at Eastern Creek Raceway with a virtually unbeatable lead. In the end he collected his second championship in the opening Saturday night race and then went on to clean-sweep the round in record-breaking style in his Pirtek Falcon. This was the first time Ford had won back-to-back titles since 1988-89. Teammate Russell Ingall also drove a superb final round to finish second in the championship, giving Stone Brothers Racing a memorable 1-2 Quinella finish.
Ambrose won the coveted Barry Sheene Medal in 2003 and 2004.
He started 2005 the way he ended 2004 with a clean sweep of the opening round in Adelaide. He remained in the championship lead until Round 10 at the Bathurst 1000 when he was involved in a controversial crash with Greg Murphy approaching The Cutting on the way up 'The Mountain' late in the race. The two drivers, infuriated with one another, shared some heated words after the crash.
Greg's probably going to blame me, because he tends to blame everyone but himself for these kinds of incidents. I knew that I was already 99% past him, I gave him a car-length and a half to go two-wide up into The Cutting, and I just got clean wiped out.|30px|30px|Marcos Ambrose|on a TV Interview after Bathurst 2005
This crash, combined with a poor performance at the co-hosted (with the Champ Cars) round on the Gold Coast arguably lost him a third straight title. He thereafter supported teammate Russell Ingall's title bid successfully, and the two helped Ford and Stone Brothers Racing take the Drivers, Teams, and Manufacturer's championships. Ambrose finished third in the championship behind Ingall and fellow Ford driver, and good friend Craig Lowndes.
Marcos is still the only driver to have a round win in every V8 Supercar season he has participated in.
The Ford Motor Company signed Ambrose to participate overseas in the United States with Wood Brothers/JTG Racing in the NASCAR Craftsman Truck Series in 2006. However, Ambrose had to wait until part way through the 2006 season to begin. NASCAR did not clear Ambrose to race the NCTS' first three races, as they were held on intermediate to high-speed ovals, and like fellow Wood Brothers/JTG Racing driver Bobby East, Ambrose was not cleared to start in the faster races. Ambrose made his Truck Series debut on April 1 2006 at the Kroger 250 at Martinsville Speedway, qualifying 20th and finishing 33rd after being caught up in an incident unfolding in front of him.
Ambrose is the first notable Australian driver in a NASCAR series event since Dick Johnson in 1990.
Ambrose made history by finishing third in the O'Reilly Auto Parts 250 at Kansas Speedway on July 2, 2006. This was the first time a non-American driver has finished in the top five of a truck series event since Canadian Ron Fellows won on the Watkins Glen road course on June 26, 1999. He also took the lead in the opening laps, becoming the first Australian to lead laps in NASCAR Craftsman Truck Series competition. The next week, he made further history by scoring his first Bud pole position for the Built Ford Tough 225 at Kentucky Speedway, and then leading the most laps in the race itself, though he finished 19th. Ambrose scored his second podium result of his debut Craftsman Truck Series season, finishing 3rd in the Toyota Tundra 200 at Nashville Superspeedway after qualifying 11th.
Ambrose reached as high as 19th in the championship points, but finished the season 21st overall and 3rd in the Rookie of the Year standings, despite having missed the first three races of the year.
Ambrose got his first Nationwide Series win on August 9, 2008 in the Zippo 200 at Watkins Glen. The next day, he finished 3rd, after starting in 43rd position, in the Centurion Boats at the Glen, behind winner Kyle Busch and Tony Stewart.
| Season | Series | Position | Car | Team |
|---|---|---|---|---|
| 1996 | Australian Formula Ford Championship | 4th | Swift SC95K Ford | |
| 1997 | Australian Formula Ford Championship | 2nd | Van Diemen RF97 Ford | |
| 1998 | British Formula Ford Championship | 5th | Van Diemen RF98 Ford | Van Diemen |
| 1999 | British Formula Ford Championship | 3rd | Van Diemen RF99 Ford | Van Diemen |
| 1999 | Formula Ford Euro Cup | 1st | Van Diemen RF99 Ford | |
| 2000 | French Formula 3 Championship | 12th | Martini Mk.79 Sodemo-Renault | Mygale |
| 2000 | British Formula 3 Championship | 16th | Dallara F300 Mugen-Honda | Alan Docking Racing |
| 2001 | V8Supercar Championship Series | 8th | Ford Falcon AU | Stone Brothers Racing |
| 2002 | V8Supercar Championship Series | 3rd | Ford Falcon AU | Stone Brothers Racing |
| 2003 | V8Supercar Championship Series | 1st | Ford Falcon BA | Stone Brothers Racing |
| 2004 | V8Supercar Championship Series | 1st | Ford Falcon BA | Stone Brothers Racing |
| 2005 | V8Supercar Championship Series | 3rd | Ford Falcon BA | Stone Brothers Racing |
| 2006 | NASCAR Craftsman Truck Series | 21st | Ford F-150 | Wood Brothers/JTG Racing |
| 2007 | NASCAR Busch Series | 8th | Ford Fusion | Wood Brothers/JTG Racing |