After the “Blurred Lines” singer’s performance at the Allstate Arena in Rosemont, he joined the Baggage Claim actress for a romantic dinner at Chicago Cut Steakhouse on Saturday.
“They were kissing throughout dinner,” an onlooker tells PEOPLE. “At one point, they even stepped outside to stand over the river and hold hands.”
Thicke opted for salad and dover sole, while Patton enjoyed salad and crab legs.
“They looked very much in love,” the source adds.