Ambulances were called to Justin Bieber's Calabasas home in the early hours of Saturday morning, following a 911 call claiming that a woman had fallen unconscious during a party at the property.
According to TMZ, the woman regained consciousness before the paramedics arrived and insisted that they be called off.
The ambulances were called off some 15 minutes after the call was made at around 3am.
The 20-year-old woman did not attend a hospital but went home.
Alcohol had played a factor in the reveller's condition, according to reports.
Bieber's parties at the $6.5 million mansion, which he bought last year, generally require guests to sign a waiver before attending.
The waiver bans anyone from posting details, photos or recordings of inside his house on social-networking sites or other media.
In addition. his guests are be forbidden from talking about the "physical health, or the philosophical, spiritual or other views or characteristics" of the singer or other guests.
Anyone who breaks the waiver will be pursued for $5 million in damages, with a further $5 million fine for tweets, blogs or Instagrams.