Justin Timberlake was all over the place this weekend.

On Friday, he was in Vegas for a friend's birthday party with his No. 1 girl. No, not Jessica Biel...his mom, Lynn Harless. 

J.T. & Co. hit Dick's Last Resort, a rowdy restaurant on the Strip that makes diners wear huge paper hats. Justin wore his like a good sport as he noshed on a buffalo chicken sandwich and birthday cake.

Things took a somber turn on Sunday when the singer returned to California. Justin was just one of Cameron Diaz's ex-boyfriends who attended her late father's memorial in Seal Beach.

Nice to see the singer showing his support.