The 23-year-old American singer and 26-year-old Australian actor celebrated at an '80s-themed birthday bash for Liam's brother Luke Hemsworth, who turned 36 on Nov. 5.
Luke wore a He-Man costume to the party and shared a photo with Liam on Instagram. Liam dressed in a tight yellow tank top and red gym shorts, while Miley wore a Madonna t-shirt, skirt and strands of pearls.
"Fabulous secret powers were revealed to me the day I held aloft my magic sword and said 'by the power of greyskull!'" Luke captioned the picture.
Luke's wife, Samantha Hemsworth, model Laural Barrett and actor Mike Furze were among the other guests in attendance. Luke and his family and friends enjoyed a birthday cake inspired by Pac-Man and Rubik's Cube, according to E! News.
"Happy birthday @hemsworthluke ya legend!! #happybirthday #80s #dressup #iwasborninthe80s," Barrett captioned a group photo.
Miley and Liam reconciled in January after ending their engagement in 2013. The singer showed off her engagement ring on The Ellen DeGeneres Show in October, but admitted the 3.5 carat diamond sparkler isn't exactly her "aesthetic."
"It's very weird because this is, like, real jewelry and most of my jewelry is made out of, like, gummy bears and cotton candy," she explained.