There are no restrictions on the award, which can be given to any playwright from a first time, unpublished writer to one already established.
Mullarkey's first full length play Cannibals premiered at the Royal Exchange Manchester last year, making him at 25 the youngest playwright to have his work performed on the venue's main stage.
He was the Royal Court's writer on attachment in 2010 and has been closely associated with the theatre's international work, translating Russian and Ukrainian plays including Aleksey Scherbak's Remembrance Day in 2011.
"Harold Pinter and the Royal Court Theatre have always been gigantic inspirations to me, so I feel really honoured and grateful for the opportunity," Mullarkey commented after receiving the award last night (25 March 2014).
Royal Court artistic director Vicky Featherstone said: "Although this commission can be awarded to any playwright with no specific criteria, Harold was a staunch supporter of the Royal Court's international work and alongside his unwavering commitment to politics, it seems fitting to present Rory with the Pinter Commission. I look forward to seeing what he will make."