Paris Jackson's birthday was April 3.Evan Agostini/Invision/AP Paris Jackson celebrated her 20th birthday in the ultimate '60s-inspired ensemble. Jackson was spotted in a patterned minidress and white, knee-high go-go boots. Her birthday celebration was quite the star-studded affair with guests including Chris Brown, Paris Hilton, and Ashlee Simpson. Paris Jackson showed off her svelte figure in a '60s-inspired ensemble as she celebrated her birthday at sbe's HYDE Sunset in West Hollywood, Calif. last night. Jackson sported a barely-there, vintage minidress with a swirly purple, pink and green pattern and a plunging neckline. She paired the dress with white, knee-high go-go boots for a leggy look. Jackson's bash — a joint birthday party with manager Tom Hamilton — was a star-studded affair, bringing together celebrities such as Paris Hilton, Chris Brown and Ashlee Simpson. Hilton, whose parents, Kathy and Rick, were also in attendance, sported a lacy lilac outfit with a cardigan on top. The heiress accessorized with white sunglasses and a sparkly necklace. At the party, Jackson — who is known for her relaxed, bohemian sense of style — blew out candles on a birthday cake with a picture of her face and posed for photos with pals inside the restaurant and on the porch. Jackson's birthday was April 3, but that doesn't mean she's been partying all week long. The daughter of late legend Michael Jackson stepped out for work on Thursday night to attend the H&M Conscious Exclusive collection party in Los Angeles. For that event, the model donned a halter-top from H&M's new collection and wide-legged pants, completing her look with T-strap sandals and a patterned kimono coat.