A source close to the twosome tells E! News that while they're not an official couple (just yet), they're enjoying dating one another and taking things slow.
"They don't have a title," our insider explained. "They are having so much fun together that friends don't know at certain times if they are a couple or best friends."
The singer and model both have insanely hectic schedules to balance, but they're doing what they can to see one another whenever possible.
"They can go for a length of time without seeing each other, and then they are spending every waking moment together."
The pal close to the blossoming romance continued, "They might seem like an odd pairing, but they are quite good for each other. They've been friends forever."
So what exactly do these two see in one another?
"Patrick loves what an amazing heart she has and that she really pushed him out of his comfort zone."
E! News first reported that the famous duo had taken their friendship to the next level earlier this week.
Cyrus and her new beau stopped by Universal Studios Hollywood's Halloween Horror Nights together on Thursday along with a few mutual friends.
Schwarzenegger hasn't kept quiet about his crush on the former Disney darling, either.
Back in 2011, he told Details magazine, "My eye, though, is set on Miley."
Apparently the two went on a few dates at the time, but things ended quickly after Cyrus reconciled with her now ex-fiancé Liam Hemsworth.