Raised in Launceston, Marcos began racing karts at the age of 10 and won over 10 state karting titles before becoming the Australian karting champion in 1995.
Marcos moved into the Formula Ford ranks in 1996 and finished second in the Australian Formula Ford Championship hunt the following year. He then travelled to Europe and competed in British Formula Ford in 1998 and 1999, winning the European Formula Ford Championship in 1999 and competing in various Formula 3 titles.
At the conclusion of the 2000 racing season Ambrose returned to Australia to race with Stone Bros Racing. In 2002 he scored five pole positions, his first V8 Supercars Championship race win at Phillip Island on his way to finishing third in the championship.
Armed with a new BA Falcon in 2003, Ambrose started the season off strong with a victory in the first race of the Clipsal 500 in Adelaide. He followed it up a total of nine individual race wins and six overall round wins to claim his first V8 Supercars Championship crown.
A repeat series win in 2004 capped off two stunning V8 Supercars Championship season.
Ambrose made the decision to move to the United States and try his hand in NASCAR in the Craftsman Truck series in 2006. Ambrose ran full time in the Nationwide Series again in 2008 and drove to his first NASCAR victory on the road course at Watkins Glen International in August in his 59th career series start. Scoring his first-career NASCAR Sprint Cup Series victory at Watkins Glen for Richard Petty Racing, Ambrose ended the 2011 season in 19th position in the NASCAR Sprint Cup.
In 2014, Ambrose finished 23rd in the Sprint Cup Series point standings and compiled three, top-five and seven, top-10 finishes, as well as a NASCAR Nationwide Series win at Watkins Glen International.
In 2015 Marcos will lead the new look DJR Team Penske driving the famous #17 Ford FG X Falcon in the V8 Supercars Championship.