Brody Jenner celebrated his 30th birthday with a party in Las Vegas on Saturday, Aug. 17. Credit: Bryan Steffy/Getty

While his half-sister Kylie Jenner was busy ringing in her 16th birthday with an extravagant Alice in Wonderland-themed bash in Los Angeles on Saturday, Aug. 17, Brody Jenner marked his own birthday, the big 3-0, in slightly more adult fashion: With a celebration in Sin City!

The reality star, who turns 30 on Wednesday, Aug. 21, had a preemptive fete with a few close friends -- and fans -- at Hyde Nightclub in Bellagio on Saturday.

Jenner was "smiling a lot" and looked like he was having a great time, an onlooker tells Us Weekly. Upon arriving at the club just past midnight, he was greeted by ladies holding up signs spelling out "B-R-O-D-Y," the source says.

"Tons of girls started gathering around to try and snap a photo or see him," the source adds. 

The beach-themed party included a cake with sand and surfboards topped with a photograph of Jenner himself surfing, according to the Las Vegas Sun. At one point, the fun-loving birthday boy even grabbed a piece of cake and threw it at a friend to start a food fight. 

Jenner's rumored girlfriend, model Bryana Holly, was unable to make the bash, but a source tells Us that the pair is planning on celebrating with close friends in Los Angeles later this week.

Meanwhile, younger half-sister Kylie enjoyed a star-studded blowout at the AT&T center in Los Angeles that same night, with a guest list that included the likes of Hailee Steinfeld, Drake, Tyga, Glee's Naya Rivera, Hailey Baldwin, and beau Jaden Smith. 

Khloe and Kourtney Kardashian were both on-hand to help their younger sibling celebrate her big day, though Kim was noticeably absent (she and Kanye West had traveled to Oklahoma with baby North for West's grandfather's funeral). 

The evening -- Kylie's second bash in one week, after a family dinner at Nobu in Malibu -- even featured surprise performances by Drake and Big Sean.