Guests were given onesies adorned with Bloom's face and enjoyed a two-tier cake decorated with an owl.
Actress Jennifer Aniston and her husband, actor Justin Theroux, were among the celebrities in attendance.
"He would love to settle down with Katy and have more kids." Bloom shares 6-year-old Flynn with ex-wife Miranda Kerr, from whom he split in 2013 after three years of marriage.
Kerr has since gotten engaged to Snapchat founder Evan Spiegel.
According to the Associated Press, after five years of marriage, the couple explained the decision to split was of mutual consent, and that their priority now is to protect their children Jeronimo, 4, and Fiona, 2, during the process.
The highlight of the night for Bloom came when his mom, Sonia Copeland, made a surprise appearance.
"Best gift ever surprise visit from me mum," he captioned a photo with his mom on Instagram.
Perry and Bloom recently celebrated Christmas with the singer's family.
The couple were first linked in January 2016, and sparked engagement rumors in November after Perry was spotted wearing a massive ring on her left hand.