Smith's debut In The Lonely Hour passed one million sales in the UK in the past 24 hours, according to the Official Charts Company.
Nielsen Music confirmed that Smith had sold a million copies of his record in the US on Wednesday.
In America, only Sam Smith, Taylor Swift and the Frozen soundtrack have passed the million mark this year.
In The Lonely Hour is the second album to pass a million sales in the UK this year after Ed Sheeran's X, which achieved the figure in November.
Sam Smith told OfficialCharts.com: "Officially sold one million copies of In The Lonely Hour. To say I am ecstatic is a huge understatement.
"Thank you so much to every single person who has purchased my album."
2014 is also the first year since 2011 when more than one album has passed one million sales in the UK.
In 2011, Adele's 21 and 19, Michael Buble's Christmas and Bruno Mars' Doo-Wops & Hooligans all passed the mark.
In The Lonely Hour became the fastest-selling debut album of the year in the UK when it went straight in at number one on the Official Albums Chart in May with first week sales of 102,000.
It spent a second week at the top before returning for another fortnight 12 weeks later.
Sam Smith's album includes number one singles Money On My Mind and Stay With Me, as well as Top 10s I'm Not The Only One (number three) and Like I Can (nine).
Tracks downloaded from his album total 2.48 million, have been streamed 87 million times and viewed on video streaming sites in the UK 48 million times.
Follow @BBCNewsbeat on Twitter and Radio1Newsbeat on YouTube
Sam Smith has become the only artist to score a million-selling album in both the UK and the US this year.