The cute youngster was playing in the front yard of his grandmother Patti's house as the family celebrated the christening of Gwen's six-month-old niece Stella.
Earlier in the day he'd joined mum, dad and older brother Kingston, three, in dressing up to attend the ceremony at St Brendan Catholic Church in Los Angeles.
While the stylish tot sported a smart nautical-style shirt, dad Gavin, 44, looked dapper in a grey suit and pale yellow tie. Meanwhile mum Gwen was striking in a matching blue, black and orange striped skirt and jacket.
But back at granny's house, the blonde toddler shed his smart clothes in order to safely bomb around the garden with his dad and brother.
Ex No Doubt singer Gwen recently said that her youngest was fast revealing himself to be more outgoing than his older brother.
"Zuma is more of a show-off. He wants everyone to watch him, and he's a goofball, and he's really silly. He's a funny guy," said the 40-year-old.