Murs will open the week-long series of shows at St John-at-Hackney Church on November 20 and will be supported by Lawson and Loveable Rogues.
Macdonald will play a headline set on November 25 and will be supported by Karin Park and some yet-to-be-announced special guests.
Richard Hawley, The Maccabees and Noah and the Whale were previously confirmed for this year's Little Noise Sessions, which aim to raise awareness of learning disability and Mencap's work.
Tickets for the newly announced show go on sale from 9am on October 31 via Ticketmaster.
Watch the music video for Olly Murs's new single 'Troublemaker' below: