The 31-year-old American singer and 39-year-old English actor brought 5-year-old Flynn to Robert Downey, Jr.'s son Exton's fourth birthday celebration Saturday. Gwyneth Paltrow and Jon Favreau were among the other celebrities in attendance.
"She looked very comfortable with Flynn and they were both smiling and happy," an eyewitness told E! News. "Flynn was having a great time and didn't want to leave the party. They stayed for several hours before they all headed back to Orlando's."
"[They] spent all day together," a source told People. "They were laughing, playing music and joking around with Flynn. They stayed at the party for hours. Katy looked very comfortable at the kids party. She seemed very happy to spend the day with Orlando."
Bloom shares Flynn with ex-wife Miranda Kerr, whom he split from in 2013 after three years of marriage. He and Perry were first linked after the Golden Globes in January and were seen together at a birthday party and a dinner last week.
"She's having fun with Orlando," an insider recently told Us Weekly magazine. "I don't think she's seeing this as long-term yet. It's a fun hookup thing right now."
Perry, who released her fourth studio album, Prism, in 2013, was last linked to her ex-boyfriend, John Mayer. Bloom last starred in Digging for Fire with Jake Johnson, and will reprise Will Turner in Pirates of the Caribbean: Dead Men Tell No Tales with Johnny Depp.