Flashbulbs were popping as the Australian actor made his red carpet debut with his beloved at the LA premiere of their new film The Last Song.
And the constant attention is something he'll have to get used to as 17-year-old Miley's other half.
In the film, Liam plays the singer's love interest. Miley's character – rebellious teen Veronica falls for the handsome beach volleyball player when she is sent to live with her dad for the summer.
Life imitated art, with the film's director Julie Anne Robinson noting the "instant chemistry" between 19-year-old Liam and his co-star.
Miley this week revealed that she started to fall for Liam when he showed his chivalrous side, opening a door for her.
The Melbourne actror has joked that life has got tough for him since she made the admission.
"There's so much pressure for me to be opening doors for everyone now," he said. "It's just too much pressure."
Others at the premiere were the new couple's co-stars Little Miss Sunshine actor Greg Kinnear, who played Miley's on-screen dad, and Kelly Preston – who portrayed her mum.
The brunette actress was supported at the unveiling by her husband John Travolta.