The romantic beach stroll was the first public sighting of the pair, since Cowell confirmed he is going to be a father.
At the world premiere of the concert film "One Direction: This Is Us" in London on Tuesday, Cowell told the BBC that "things are changing in my life right now, for the better." He added, "I'm proud to be a dad."
Cowell also said Silverman is "a very special girl" and that while he hadn't thought of fatherhood before, revealing, "Now I know I feel good about it."
Lauren and estranged husband Andrew Silverman recently settled their divorce, sharing custody of their 7-year-old son.
“X-Factor” judge Simon Cowell and pregnant Lauren Silverman, looked every bit the happy couple as they smiled widely and held hands in St. Tropez on Saturday. Check out the pics here.