The band announced they would play their only UK show of 2011 at the Hackney Empire on October 25.
Tickets went on sale at 9am this morning and sold out within 60 seconds, with many fans failing to book seats.
The show will be one of the first opportunities for fans to hear material from the group's forthcoming Ceremonials album.
The record is the follow-up to 2009's Lungs and will feature Florence + the Machine's new single 'Shake It Out' and their buzz track 'What The Water Gave Me'.
Ceremonials will be released in the UK on October 31, while 'Shake It Out' is available to download now.
Meanwhile, Channel 4 has confirmed that it will be filming the one-off concert and broadcasting it on T4 in early November.
> Florence + the Machine's new album 'Ceremonials' - First listen
Watch the music video for Florence + the Machine's new single 'Shake It Out' below: