It's understood the duo will work together on a different venture, although more details were not provided at the time of writing.
Both depart after almost five-and-a-half years. Moroney, head of insight and strategy, joined Mischief from Citizen, initially as planning director. Statt, executive creative director, was formerly a director at Frank PR.
In a statement for PRWeek, Moroney and Statt said: "Leaving Mischief is a decision we didn’t take lightly. New decade, new challenge. Watch this space..."
Statt's last day at Mischief is today (Thursday) and Moroney is to leave next month.
The news comes amid the continued integration of Mischief and its Engine stablemate MHP. Last year it was announced that both agencies would run under the Engine banner, although with the two names retained.
Since then, changes have included integrating the Mischief and MHP creative services into a centralised hub.
Alex Bigg, CEO of MHP, said: "Gemma and Damon have made a significant contribution to Mischief over the years and we wish them well with their new venture. Planning & creative remains at the heart of Mischief and we will soon be announcing a number of new hires bolstering what is already an exceptionally strong team of creatives and strategists."
Their departure follows other significant personnel changes at Mischief and MHP in recent months, with the departure of Mischief CEO Frankie Cory and the promotion of creative director Greg Jones to Mischief MD.