The actor also sent Mother's Day wishes to his own mom, Christine Anne Boldt.
The Triple Frontier star, who shares 13-year-old Violet, 10-year-old Seraphina and 7-year-old Samuel with Garner, took to Instagram on Sunday to pay tribute to his ex, as well as his own mother, Christine Anne Boldt.
"Happy Mother’s Day to the two incredible mothers who have shown me the meaning of love," Affleck wrote alongside pics of Garner with Boldt and a throwback of himself with his mom. "Today I am making donations to two organizations in their honor: @cut50’s #DignityForIncarceratedWomen campaign, a national initiative to help reduce the prison population while making our communities safer, and @NationalBailout, an incredible organization that works with groups all over the country on Mother’s Day to bail out black moms and caregivers, provide supportive services and fellowship opportunities to help end money bail and pretrial detention."
Affleck and Garner's divorce was finalized last November, over three years after they filed for divorce. The former couple has continued to keep things amicable, however, and are often spotted out together.
During an appearance on The Ellen DeGeneres Show last month, Garner -- who is now dating CEO John Miller -- opened up about a recent tabloid rumor which claimed both she and pal Reese Witherspoon were pregnant. According to the actress, her three children with Affleck have completed her family.
"To be clear, again, I'm 47," she stressed. "We've wrapped it up, we're not doing it."
"Reese on the other hand, she might be ... she's definitely pregnant," Garner cracked. "She's having twins!"
See more in the video below.