On Saturday, March 2, the two were seen ringside watching the UFC 235 fight in Las Vegas, where Efron was photographed laughing as the camera panned to him with Bro sitting alongside the actor.
An eyewitness at the fight told E! News that Efron and Bro arrived at the event together and "looked like they were having a great time." The source added the two were "smiling and laughing in their seats" before the show.
"Zac was approached by multiple fans and Sarah was very patient as Zac spoke to everyone who approached him," the witness said, adding that the couple were "not overly publicly affectionate" and that they "weren't doing anything to attract any additional attention." Efron and Bro left T-Mobile Arena together after the fight.
In January, the two were seen at a fitness class in Los Angeles, and on March 1, both Efron and Bro separately shared photos of a night spent watching a Los Angeles Kings hockey game at the Staples Center in Los Angeles, though it's unclear whether they attended the game together.
"@lakings in overtime #freehockey," Efron wrote alongside a selfie in which he pulled a Kings hat low over his eyes. Meanwhile, Bro posted a photo of herself in the Kings' locker room wearing a hockey jersey with her name on it.
"Thank you @lakings for making my first hockey game something very special I'm already a fan!" she wrote.
Bro is a Danish swimmer who competed in the 2016 Olympics in Rio when she swam in the 4x100 meter relay.
Efron is currently recovering from a torn ACL and subsequent surgery, sharing the news of his injury last month with an Instagram photo of himself in a hospital bed with a brace on his leg.
"I tore my ACL shredding the gnar," he wrote, "but all is good. I opted for surgery so I can come back stronger than ever. Thank you to Dr. Kvitne and his team at Kerlan-Jobe Surgery Center. I'll keep you updated as I heal and progress! Thanks for all the love and positivity!"
The Extremely Wicked, Shockingly Evil and Vile star previously dated his High School Musical co-star Vanessa Hudgens from 2007-2010, Michelle Rodriguez from June to August 2014 and he was linked to his Baywatch co-star Alexandra Daddario in 2018.
Photo Credit: Getty / Rich Polk