The former That 70s Show costars have become almost inseparable in recent weeks.
As RadarOnline.com reported, the two were arm-in-arm when they went to lunch together on June 30.
Demi Moore's estranged husband and the Ted star have also been off motorcycle riding together.
But playing it coy, Mila told the August issue of Elle magazine, "I am totally single... Listen, we hang out. We've known each other for 15 years. We have mutual friends. We're comfortable with one another."