The 31-year-old actress took to Twitter.com to let followers in on the happy news, flashing the ring her toyboy lover has given her in an accompanying photo.
She wrote, "So this just happened..." while Dykstra tweeted, "She said yes!!"
Dykstra, 23, who posted the same picture, is the son of former New York Mets star Lenny Dykstra.
This will be Sigler's second trip down the aisle - she ended her two-year marriage to her manager A.J. DiScala in 2005.