Rex USA 1 / 10

Justin Timberlake still knows how to compliment a lady. Okay, that's probably not a news flash.

During his recent Las Vegas show, the "Not A Bad Thing" singer was speaking to the crowd when a brunette woman told him that she listens to him every week during chemotherapy. Timberlake began applauding the woman, encouraging the sold out crowd at MGM Grand Garden Arena to cheer for a cancer survivor.

RELATED: Celebrity beach cruising

Timberlake, an acoustic guitar in his hand, began complimenting the woman while tuning his guitar.

RELATED: Hot stars looking nerdy

"That hair is looking good. You look good, you look real good. If I wasn't married, I'm just saying," he joked before singing "Señorita."

RELATED: Hottest beach couples

We don't think wife Jessica Biel has anything to worry about, but Timberlake can certainly flirt with the best of them. During the same show, attended by prized boxer Floyd Mayweather Jr., Timberlake also sang "Happy Birthday" to a girl in the front row. When the girl began getting emotional, he told her, "Don't cry. You can do that later, at like 3 a.m. but don't cry right now."