Post Malone shocks fans as The Kid Laroi joins him on stage to perform at his concert in Sydney

• READ MORE: Post Malone smokes a cigarette in cat pyjamas as he's swamped by fans after jetting into Sydney Airport amid Australian tour 

The Kid Laroi shocked fans as he joined Post Malone on stage at his Sydney concert on Thursday night.

With a beanie pulled down low over his head, the 20-year-old rapper, whose real name is Charlton Kenneth Jeffrey Howard, belted out his heart to a screaming crowd.

Laroi rugged up in a baggy white T-shirt, trench coat and loose jeans as he fired up the crowd.

The audience were shocked when Malone, 28, real name Austin Richard Post, called the Aussie out on stage and embraced him. 

Malone stripped down to his iconic jean shorts and went shirtless, as he often does while performing.

At one point, the Sunflower hitmaker pulled out his acoustic guitar and sat down on stage with his fellow singer-songwriter.

The duo brought the energy down, singing sweet melodies as they relaxed with their fans.

Laroi's appearance on stage came as a huge shock to fans who were expecting to see him in Australia for his First Time tour in February.

He'll kick off his tour in Melbourne before heading to Perth, Adelaide, Sydney and the Gold Coast.

'I'm so excited to be coming back home in February,' the Australian rap sensation recently said.

'I felt so much love from the fans on last year's tour — it's something I'll never forget. I can't wait for you to all see this new show — we've taken things to a whole new level.

'I love you and I'll see you all really soon.'

Meanwhile, Post Malone is currently travelling the world for his If Y'all Weren't Here, I'd Be Crying Tour.

He is set to perform in Victoria on Saturday night before heading to Perth for his final show on Sunday.

The US singer kicked off his sets Down Under in Brisbane last Thursday night, and participated in a great, yet disgusting Aussie tradition - the 'shoey'.