The streaming event in aid of Focus Ireland will see him perform from Belfast, with other artists in Dublin’s Olympia Theatre and Windmill Lane Recording Studios.
Acts taking part include Pillow Queens, Gilbert O’Sullivan, Aslan, Blindboy Boatclub and Tolü Makay.
McMullan’s performance comes ahead of the release of a new feature length documentary about his rise to fame from 2015 to 2019.
In an interview with The Times, the 31-year-old spoke of how his life changed when fellow musician Foy Vance offered him an opening spot on his tour, which led to a career-making support slot with Ed Sheeran.
On his friendship with Sheeran, he said: “He’s a sweetheart and if I ever needed to talk about anything he’s there, and that says a lot about him, considering there’s a lot more people higher up in the ranks than me that would be dying for his attention.
“Not that I would ever plague him, but I just reach out and say hello and he’s always asking how I’m doing, how’s life, and we’ll talk a wee bit about music. I’m grateful he’s part of my life.”
The documentary will premiere at the Galway Film Fleadh at the end of next month before a limited cinema release in August and September.
With the expected return of live music, a full tour of Ireland and the UK beginning at the Millenium Forum in Londonderry in September is also on the cards.
As well as McMullan’s set from Belfast, Rock Against Homelessness will also see guitar duo Rodrigo y Gabriela performing from Mexico, while Ken Griffin will play with The High Leaves in New York.
Tickets for the concert are priced at €23 (£19.75) from ticketmaster.ie and it will be available to view for seven days after the event.
Aslan frontman Christy Dignam said: “It’s a cause that’s very close to our hearts.
“But for the grace of God it could be any of us, and the pandemic showed us how any life can be turned upside down in an instant.”
Oscar-winning director Jim Sheridan, who will be interviewed onstage about homelessness, said: “With the homeless, it’s almost like you need to see scenes of them being driven out of their homes for it to really strike a chord with Irish people.
“You don’t see that, how they lost their home. All you see is the result; you’re not seeing whether it was the banks, or what caused them to be on the street. We need to examine the root causes of homelessness and what it was that brought them to that place.”
Peter Vandermeersch, publisher at Mediahuis Ireland, described homelessness as “one of the most urgent issues in this society”.
“On the independent.ie and in our various print titles, we continually write about this issue but by organising this concert we want to do a bit more than write about it,” he said.
“We want to enhance the awareness and raise some money for Focus Ireland. Because nobody in this country should be without that place that we all call home.”