The singer released a reworked rendition of Shontelle's 'Impossible' following his win on the singing show back in December.
The track shot to number one in the UK and has sold over 1.3 million copies in his homeland alone since its release.
However, 'Impossible' has also had surprising success across the world after being serviced as a single in other territories.
Arthur has reached number one in Spain, Greece, Ireland, Luxembourg, Slovakia and the Czech Republic with 'Impossible'.
The track has also hit number two in Australia, New Zealand and Switzerland, while going top five in Belgium, Austria and Germany.
It has also peaked at number ten on the French single chart, with the global success making it one of the best-performing winner's single internationally from a UK X Factor winner.
'Impossible' is still performing well on iTunes sales charts in France, Luxembourg and Greece, meaning the star could sell further copies still.
Arthur is currently working on his debut album, which is expected to be released in the UK later this year.
Watch the music video for James Arthur's 'Impossible' below: