The former Buffy the Vampire Slayer stars posed for an Instagram photo over the weekend, when Gellar attended Hannigan's daughter's birthday party in Santa Monica.
"So this girl (#AlysonHannigan) and her husband (#AlexisDenisof) know how to throw a party," Gellar captioned the photo. "I thought I was good with the crafts, till I went to this party #CraftMaster."
"Thanks for having the #PrinzeFamily I've never seen a farm and pony rides in Santa Monica before #NowIveSeenItAll," she added.
The mini-reunion comes just weeks after Hannigan tweeted that she ran into Gellar at a Michaels craft store.
"I had a lovely time with @SarahMGellar when I ran into her at Michaels today. Our mutual love of crafting would make Willow happy I think," Hannigan wrote.
Hannigan and her husband, actor Alexis Denisof, have two daughters, Satyana and Keeva, who turned 3 on May 23. Gellar and her husband, Freddie Prinze Jr., have two children, Charlotte and Rocky.