The auction will feature 148 pieces of urban art from acclaimed street artists including Banksy, Shepard Fairey and Nick Walter.
Traditionally a travel and leisure agency, Siren said the move reflected the agency’s decision to expand its services beyond traditional PR.
Earlier this month Siren PR announced that it had rebranded to Siren Communications 'to better reflect the wider range of services it is now undertaking for clients'.
‘This win reflects our decision to expand our services. We’re now offering clients more than traditional media relations,’ said consumer director Victoria Savill.
As part of the brief from Dreweatts, Siren will host the online auction through its digital offering as well as working to raise awareness of the auction, which runs until 6 December.
Commenting on Dreweatts' first online urban art sale, director of urban and contemporary art at the auction house Mary McCarthy said: ‘We’ve gathered together a fantastic collection of urban art and are excited to team up with Siren Communications to help raise awareness of this sale.’