The 'Wow' hitmaker was midway through her set at Radio 2 Live in Hyde Park when she began singing their 1988 duet 'Especially For You' with a choir, but after the second chorus, she delighted the London audience by saying she was in need of a ''dance partner'' - prompting her former boyfriend to walk out on stage.
Jason took Kylie in his arms and they swayed back and forth before he joined her on the mic for the song's finale.
Kylie laughed afterwards: ''He didn't know that was going to happen.''
And after leaving the stage, Jason, 50, confirmed the moment hadn't been planned but he had ''loved every second''.
He said: ''I literally turned up on my bike to support my friend @kylieminogue and next thing you know I'm onstage @BBCRadio2 Hyde Park in front of 70,000 people recreating those dance moves Especially For You 1988 .. mad! Loved every second. Thank you for all your support. Memories = magic (sic)''
And Jason wasn't the only surprise guest of the evening as shortly afterwards, Rick Astley joined Kylie on stage to sing his 1987 single 'Never Gonna Give You Up'.
After the song finished, the 50-year-old singer told her guest: ''I don't want to give you up or let you go.''
Rick then took on Robbie Williams' vocals from his and Kylie's 2000 duet 'Kids'.
Kylie's set spanned her entire career, from an acoustic version of her debut single 'I Should Be So Lucky' right up to tracks from her latest record 'Golden'.
And when a technical hitch meant she had to fill in some time, Kylie delighted the crowd with snatched a capella versions of 'Got To Be Certain', 'Step Back In Time' and 'Je Ne Sais Pas Pourquoi', before getting back on track with 'In Your Eyes'.
With the Jonas Brothers, Westlife and Backstreet Boys getting back together recently, we should hardly be surprised that New Kids on the Block are...
Our all-time favourite Prodigy songs from their entire back catalogue.
In memory of Keith Flint, we look over at some of his iconic moments caught on camera.
If there was ever a reason for you to try something fresh and new then Poppy Ackroyd is surely it.
The New Zealand musician is a big fan of the Emerald Isle.
An exclusive interview with ambient folk artist Runah.
Are they in love or just incredible actors?
Pablo Honey was released on this day (February 22) in 1993.
Set up as an old-style disaster movie with only a fraction of the plot, this...
California is well-known for playing host to regular earthquakes, being located right on top of...
Far from the standard biographical documentary, this is a strikingly artistic exploration of the life...
In true Nick Cave style, the lines between real-life and fiction are blurred in a...
Indescribably insane, this outrageously inventive French drama is so bracingly strange that we can't help...