1989 - 1995
Marcos commenced motor racing career in karting at the age of 12. He won four Tasmanian titles in juniors before taking on senior competition at the age of 16. In seniors in 1995, Marcos won three Tasmanian titles, a Victorian title and the prestigious Australian title in Dubbo, New South Wales. His success in 1995 included winning every major karting meeting in Tasmania.

1996
1996 saw his first foray into open-wheel racing competition in the Australian Formula Ford Championship finishing an astonishing fourth in the series.

1997
In 1997 Marcos continued his stellar progression with a runner-up finish in the Australian Formula Ford Championship.

1998
A move to the UK followed in 1998 with competition in the British Formula Ford Championship with the Van Diemen Team, and a fifth placed finish for the year.

1999
Won the coveted European Formula Ford Championship in 1999, and placed third in the British Formula Ford Championship as well that year.

2000
Won the Motor Sports Achiever of the Year and Young Achiever of the Year awards at the Australian Motor Sports Awards in February 2000.

Raced in the French Formula 3 competition before withdrawing mid-season and hooking up with Alan Docking Racing for the concluding rounds of the British Formula 3 series.

At the end of 2000 he was back in Australia and won the Young Guns race at the Gold Coast Indy 300 against 'mates' David Besnard, Steve Johnson and Paul Weel.

2001
Marcos returned to Australia and debuted in the V8 Supercar Series in 2001 with Stone Brothers Racing in the Pirtek-sponsored Ford Falcon.

In his first ever race in a V8 Supercar at the Australian Grand Prix in Melbourne in 2001, Marcos put his Pirtek Falcon on pole position. This was a non-points scoring round in the V8 Supercar Series.

His first championship pole position was in Round 3 at Eastern Creek, NSW in 2001, which was only his third-ever championship round in a V8 Supercar.

Marcos claimed his first round win in Round 4 at Hidden Valley in the Northern Territory in 2001.

His first season in a Ford V8 Supercar produced an eighth placed series finish and the honour of being awarded the V8 Rookie of the Year and CAMS Personality of the Year for 2001.

2002
2002 started brightly for Marcos with the 'Devil Racer' claiming his first ever V8 race win (not round win) in race one at Phillip Island (Round Two).

Marcos finished the year in style by winning both races at Sandown (Round 13) catapulting him to outright third in the series. He was the highest placed Ford driver in the series - an amazing result for a driver in only his second year of V8 racing.

His year included five pole positions (equal highest in the season with Mark Skaife) and five round podium finishes including the win at Sandown.

There was 29 races in 2002 and Marcos achieved a top-three finish in 12 and was the leading Ford driver in 16 races.

2003
In 2003 Ambrose claimed his maiden V8 Supercar Championship, recording an amazing 6 Round wins from 13 Rounds to finish 102 points clear of second place.

Marcos claimed a race win in the first race of the season at the Clipsal 500 in Adelaide before claiming his third career round win and first round win for the season at Eastern Creak Raceway.

Marcos finished the season winning the Pole Position Award for claiming pole five times in the season and claiming the inaugural Barry Sheene Medal for his outstanding leadership, personality, fan appeal and sportsmanship.

The championship win was also significant for Ford, with Marcos bringing the blue oval its first V8 Supercar Championship since 1997.

2004
Marcos secured back-to-back V8 Supercar Championships in 2004, clinching his second title with a clean sweep of the final round of the season at Eastern Creek Raceway. He claimed six round wins and three pole positions on his way to the title and once again won the coveted Barry Sheene Medal. This was the first back-to-back title for a Ford driver since 1988-89.

2005
Marcos was once again the leading driver in the V8 Supercar Championship, winning the first round at the Clipsal 500 at Adelaide and leading the championship until Round 10 at the Supercheap Auto Bathurst 1000. A controversial crash in the latter stages of the race led to a DNF and dented his aspirations for a third consecutive championship.

Ambrose eventually finished third in the championship, won by his team-mate Russell Ingall. His strong performances alongside Russell Ingall and Craig Lowndes secured a third straight manufacturers championship for Ford.

2006
At the first V8 Supercar race of 2005 Marcos announced his intention to become the first Australian to compete full-time in NASCAR.

The Ford Motor Company signed Marcos to compete in the United States with the Wood Brothers/JTG Racing operation in the NASCAR Craftsman Truck Series.

Marcos had immediate success in the category winning his first Budweiser Pole at Kentucky Speedway on July 8, which was the first time a foreign-born driver had won a series pole since June 26, 1999.

He is the first Australian to lead laps in the NASCAR Craftsman Truck Series and the first Raybestos Rookie of the Year candidate to win pole since November 2004 when David Reutimann captured the No. 1 starting position at Homestead-Miami Speedway.

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 backed this up with another third place finish at the Nashville Superspeedway on August 12, becoming the first Truck Series rookie to gain two top five finishes in 2006.

2007
Ambrose made history in 2007, becoming the first non-North American driver to finish in the top 10 of a NASCAR championship (NSCS, NNS, NCTS) with eighth overall in his rookie season in the NASCAR Nationwide Series (formerly NASCAR Busch Series). Ambrose was second to fellow Ford driver David Ragan in the Raybestos Rookie of the Year standings and achieved a best finish of fourth along with pole position at Memphis in November.
 
During 2007 Ambrose achieved six top 10 and 19 top 20 finishes but undoubtedly the highest-profile moment of the year came in Montreal, Canada, when Ambrose dominated the race only to be taken out of the race by Robby Gordon with a few laps remaining. Ambrose led more laps than any other driver and was on his way to his debut NASCAR win until the Gordon incident.
 
As a result of the clash Gordon was suspended from the following day’s NASCAR Nextel Cup event, but as a gesture of goodwill, Gordon offered Ambrose a drive in one of his Cup cars for the following weekend’s Cup race at Watkins Glen. Unfortunately Ambrose was denied the chance to qualify for the race when qualifying was rained out and the field set on championship owner’s points.

2008
2008 saw Ambrose again suit up for a full season in the Nationwide Series and like 2007, Ambrose finished the season in the top 10 in the series points score.

The undoubted highlight was Ambrose’s sensational win on the Watkins Glen road course in the spectacular STP livery of the #59 Ford Fusion. It came just one week after Ambrose dominated the Montreal event for the second-consecutive year, only to be denied the win, this time by torrential rain.

The Watkins Glen win made Ambrose just the second non-North American to win a NASCAR event, after former Formula One driver and Columbian Juan Pablo Montoya, who claimed two wins in 2007.

The 2008 season also saw Ambrose make his Sprint Cup debut, running as high as second in his first race at the top level before gearbox failure on the Sonoma road course.