The 'Wrecking Ball' hitmaker, who split from her 'The Hunger Games' star fiance Liam Hemsworth last September, spent time with 'The Dallas Buyers Club' star at his home in Los Angeles earlier this month.
A source told Us Weekly magazine: ''(They) are hooking up. She stayed over at his house in L.A. in early February.''
The 30 Seconds to Mars frontman was photographed catching up with Miley at Clive Davis' pre-Grammy Awards party late last month and they have developed a close bond.
An insider said: ''They like to have a good time, they love to talk about art and music -- and they're both comfortable with nudity!''
But a friend close to Jared insisted his romance with Miley, who kicked off the US leg of her 'Bangerz' world tour last weekend, isn't serious, explaining: ''Jared doesn't do girlfriends.''
The actor recently sparked rumours he was dating '12 Years a Slave' star Lupita Nyong'o after they were seen getting cosy at the Crosby Street Hotel in New York City last week.
An eyewitness previously said: ''They were huddled at a corner table together looking very close.''
Martha is soon caught in the middle of a hitman war.
It's been 15 years since Zoolander hit movie screens in 2001.
Rebel Wilson has taken the world by storm after arriving in America five years ago.