Both acts have been confirmed to play all three of the festival's dates.
The Dot to Dot event is spread over three venues and three days. Opening in Bristol on May 28, it then moves to Nottingham for May 29 and concludes on May 30 in Manchester.
Other acts due to perform include Hurts, The Joy Formidable and The Naked & Famous.
Tickets are on sale now.
We Are Scientists previously announced that they are to embark on a UK tour this June, while Guillemots are also to play the Hop Farm and Wilderness festivals.
Watch the video for We Are Scientists' 2008 single 'After Hours' below.