The 23-year-old 'Rolling In The Deep' hitmaker's second album, which released in January 2011 has sold 4,274,300 copies in Britain, 500 more than the late singer's 1982 classic record, reported Daily Mail online.
The huge success of the album has made it to the fifth best-selling album of all time in the UK.
"To add to her many landmark records, Adele's achievement in overtaking 'Thriller' in the all-time sales list is truly remarkable. 'Thriller' has long been recognised as one of the most iconic albums of all time, there is now no doubt that '21' can be spoken of in the same breath," said Martin Talbot, MD, Official Charts Company.
According to the organisation, '21', which has spent 23 weeks at the top of the UK singles chart ,continues to sell around 20,000 copies a week.
To date, 'Thriller' has sold more than 100 million copies worldwide while '21' has clocked up global sales of around 20 million.