Kunis, 28, attended the Greenville, N.C., event Friday with Sgt. Scott Moore, who asked her out to the ball via YouTube over the summer.
"Everything went well," Capt. Scott Sasser, a spokesman, told Access Hollywood. "It was a great experience for everybody."
Timberlake may have also received a YouTube invite to the Marine Corps Ball, but it was Sgt. Moore who started things with his July video. "Hey, Mila. It's Sergeant Moore, but you can call me Scott," he said from a base in Afghanistan. "I just wanted to take a moment out of my day to invite you to the Marine Corps Ball ... with yours truly. So take a second, think about it and get back to me."
Moore's unit recently returned from a seven-month deployment.
Timberlake, who attended a similar event last weekend with Cpl. Kelsey De Santis, later wrote on his blog that the ball "turned out to be one of the most moving evenings I've ever had."