The actress got together with a few of her closest friends for an intimate dinner party at her Los Angeles home on Sunday.
Eating outside on a large patio decorated with vintage, one-of-a-kind furniture pieces, Garner and about 30 guests chatted and sipped on cocktails before sitting down for a full-course dinner as the sun began to set.
"There was a lot of laughter. Everyone seemed to have fun," a source tells PEOPLE. "Soft music played during the dinner. It was a quiet party and the last guests left by 11 p.m."
But what would a birthday party be without a little entertainment?
The night featured a surprise performance by a live marching band. When they arrived, Garner was heard laughing and squealing with excitement.
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She was also surprised with presents including bouquets of both balloons and flowers.
While Garner enjoyed her party, Ben Affleck took their three kids, Violet, 10, Seraphina, 7, and Samuel, 4, for an early dinner at a restaurant in L.A.