The 30-year-old actress came out on top of the Lycos XY poll of more than 1,000 men 20 months after giving birth to her daughter Gracie, Sky News reported.
Following behind Beckham in the poll's results was British pop star Jamelia, while 33-year-old German supermodel Heidi Klum took fourth overall.
British actresses Donna Air and Elizabeth Hurley took sixth and eighth place respectively on the sexy mother list.
A Lycos XY spokesman said that the poll's findings showed that motherhood doesn't mean an end to attractiveness.
"It's great to see successful, beautiful women flying the flag for mums everywhere," he told Sky News. "The glamorous world of celebrity is a long way removed from the lives of most of us, but perhaps that's why we love these career-and-child-juggling women so much."