Published Wednesday, 04 June 2014
The pair recorded the duet for music video website Vevo and the 22-year-old newcomer admitted he was blown away to get a chance to sing with the superstar.
He said: "Working with Mary J. Blige is one of the biggest highlights of my career so far. I remember holding her album in my hands in the car when I was a young boy.
"To meet your idols is a magical thing, but to work with them is truly a dream come true."
Blige also heaped praise on the young talent, comparing him to music greats including Luther Vandross.
She added: "I'm so honoured to have had the chance to work with Sam Smith. Sam's true soulful voice... is the first of this kind I have heard since Luther Vandross, Freddie Jackson and all the great soulful male voices from the '80s.
"I'm completely blown away by his talent, soul and the sincerity."
Smith's first album, In The Lonely Hour, became the fastest selling debut of 2014 so far when it charted at number one over the weekend.