Rod Stewart sings 'You're In My Heart' a cappella in tear-jerking video to fan fighting cancer

Sir Rod Stewart is no stranger to good deeds ...

Over the weekend the legendary rocker surprised a fan battling brain cancer with a very special performance.

Along with a brief message, the 76-year-old singer also sang a portion of his 1977 hit 'You're in My Heart' a capella to surprise a fan battling brain cancer.

"Gary, this is Rod Stewart here, all the way from London, England, where it's freezing cold," Stewart says in the video which was posted on Twitter by Good News Movement.

"I hear you're in not good health at the moment, and I also hear you're also a great fan of mine, so I'd like to do this little song for you."

After singing the song - which is Gary's favourite - Stewart closed the message by wishing his fan a merry Christmas and blew him a kiss.

Following the surprise performance, Gary responded by saying "wow" and "brilliant" before giving the thumbs up.

Good News Movement revealed that Gary's niece Jenna worked hard to connect with Stewart to bring together this special moment for her uncle.

"Good News Movement had the honour of connecting with Rod's family who immediately told us 'consider it done,'" the journalist run page said.

"They sent over this video which was shown to Gary by his sister (heard on this video) and wife (filming). Gary's family says it's the most Gary has spoken and are immensely grateful to the Stewart family."