The British hunk, who is now worth an estimated $24 million (£15 million), strapped on an apron to step behind the counter at W Mandeville in his hometown of Holmes Chapel in Cheshire, England.
Styles worked there when he was 14 years old, pulling in $9.60 (£6) an hour mopping floors and wiping down the baking trays.
A source tells Britain's Daily Mirror, "It was funny as there were security and chauffeurs and minders outside, and there Harry was acting like he was still a baker's boy earning what he earns in a second now. He posed for fans - he was just lovely."
The footage is expected to feature in One Direction's upcoming film This Is Us.