A photo posted by AJ Johnson (@theajzone) on
Blunt looked beautiful in a flowing blue and white sundress paired with a denim jacket, while Theron wore a black ensemble and looked relaxed with her hair pulled back.
The pair joined Theron's mother Gerda Martiz and friends AJ Johnson, Laini Reeves and Jenn Streicher at the party.
Johnson shared a snap of the group on Instagram along with the caption "An afternoon of love, laughs and friendship celebrating a special piece of my heart #EmilyBlunt with hostess with the mostess @charlizeafrica #CharlizeTheron."
Blunt and Krazinski welcomed their first child, a daughter named Hazel, in February 2014 and report that she's "coming around" to the idea of being a big sister.