Us Weekly revealed the cute couple alert on Thursday after sources dished the details of the latest Hollywood hookup.
A source told the entertainment magazine, "Justin is super-private about his relationships, [so] I'm not positive how they exactly met, but they've known each other for a while, when they were seeing other people."
"They recently started hanging out more, going on date-like activities," continued the insider. "They're both busy… but they're seeing where it goes."
One thing that drew the two of them together is their "similar sense of humor."
Seyfried has had a busy summer promoting her new film Lovelace, but it sounds like Long has been there every step of the way. He even attended the premiere on July 30.
The source revealed, "Justin came alone and stayed close to Amanda all night. They weren't making out or anything like that, but they were just inseparable during the event. He hung out when she talked with others."
He's also playing a supportive role by touting his new flame's talents on Twitter.
The two are keeping a low profile since they've both experienced high-profile romances in the past. The 27-year-old actress dated her Mamma Mia! co-star Dominic Cooper for three years while the 35-year-old iSteve star dated Drew Barrymore on and off for over three years.
Let's see if they're able to keep their budding love private and away from the prying paparazzi's lenses.
And you'll see personalized content just for you whenever you click the My Feed .
SheKnows is making some changes!