The pair, who have been spotted hanging out several times already this month, spent all day together on Saturday, reported People magazine.
"They attended a kids' birthday party at Robert Downey Jr's house with Orlando's son Flynn. Katy even sat in the back of the car with Flynn when Orlando drove them to the party," a source said.
Perry, 31, and Bloom, 39 - who shares Flynn with wife ex Miranda Kerr - were first seen mingling at the Weinstein Co and Netflix Golden Globes afterparty in January, and already look "so happy" together.