The singer's debut album Our Version of Events also tops the list as their most-downloaded album of 2012.
She said: "To hear that I'm iTunes 'Artist of the Year' and that Our Version of Events was the best-selling album on iTunes this year is just incredible!
"Thank you for all your support and making this year even more special."
Meanwhile, Gotye and Kimbra's 'Somebody That I Used to Know' is the best-selling song of the year, while Carly Rae Jepsen's 'Call Me Maybe' was named the site's 'Song of the Year'.
Lianne La Havas's Is Your Love Big Enough? is listed as their 'Album of the Year', and 'Performance of the Year' was awarded to Isle of Wonder: Music for the Opening Ceremony at the London Olympics.
It was recently reported that Sandé has claimed the overall best-selling album of 2012 so far, having shifted almost one million copies to date.
Watch the music video for the star's latest single 'Clown' below: