The musician - who became the first artist ever to scoop the award twice earlier this week - appeared on stage just before 8pm, opening her set with 'Let England Shake' and 'The Words That Maketh Murder'.
Dressed all in black and sporting a feathered headdress similar to the one she wore at the Mercury Prize ceremony on Tuesday evening, Harvey performed on an undecorated, uncluttered stage with minimal lighting and three backing musicians.
She spoke only once to thank fans after her closing track 'Meet Ze Monsta', saying: "Thank you very, very much. Thank you for listening. I hope you have a wonderful evening. You look great! Goodnight!"
Many of the festival's 50,000 guests embraced Bestival's official fancy dress theme of 'popstars, rock stars and divas' during the day as the weather remained fair. However, rain has been forecast for the festival's final day tomorrow.
The Cure will headline tonight's Main Stage programme with a two-and-a-half hour set, while Mercury Prize nominees Metronomy are due to play a late show in the early hours of Sunday morning.
> Bestival 2011: PJ Harvey, The La's, Santigold in pictures