Nicole Richie celebrated her 35th birthday with a disco-themed party.

Nicole Richie

Nicole Richie

The 'Simple Life' star was joined by celebrity pals including her sister-in-law Cameron Diaz, Kate Hudson and Jessica Alba at the event in Los Angeles.

Sharing a snap of herself and Nicole at the party, Kate wrote: "Happy birthday gorgeous! @nicolerichie #DiscoNight (sic)"

Jessica also shared a number of pictures from the party, writing: "#aboutlastnight #selfielessons @nicolerichie #disco (sic)"

Meanwhile, the 35-year-old star has been busy as she recently took her children on tour with her husband Joel Madden and admitted they were having trouble sleeping.

She said: "I was very quiet around my kids when they were babies and now they're light sleepers. I wish I had been a little more rough with them.

"I had two friends that were moms before me - I had kids very young. It was really so refreshing to see two women that have such different taste and parenting styles maintain a friendship and not judge each other for the way that they bring up their kids.

"That's something that's always stuck with me because there's not one way to raise children. There's no one right way to be a mother. It depends on your house and lifestyle. The biggest lesson I've learned is not to judge!"