Over the past seven years at the PRCA, Cartmell led the body through issues including the Bell Pottinger scandal and the successful Supreme Court battle with the Newspaper Licensing Agency over online coverage fees. He also oversaw a corporate rebrand for the PRCA.
Cartmell worked as communications, marketing and events director before being promoted to the additional role of deputy director general in 2018.
"The last seven years have been something of a whirlwind. Huge thanks to Francis for taking a chance on an unkempt journalist lured by the promise of unlimited curry," Cartmell said.
"I'm proud of our campaigning work around diversity, payment of interns, and the gender pay gap, and I leave a hugely talented team behind. We’ve grown to be the largest PR association in the world, and I’m sure the PRCA’s growth with continue unabated.
"Having worked on some high-profile issues, I’m looking forward to providing content creation and PR services to communications, digital, media, and publishing companies."
PRCA director general Francis Ingham said: "It’s been a huge pleasure to work with Matt over the past seven years. We’ve travelled the UK together; heard and indeed given both excellent and execrable presentations; handed over hundreds of awards; and worked hand-in-glove to transform the PRCA, and to advance the interests of an industry to which Matt now returns as a practitioner.
"We will miss him, his Sutton Coldfield meets Southwark vowels, and his green suits very much indeed."
Before working at the PRCA, Cartmell worked on the editorial team of PRWeek, rising to the role of news editor. He has also worked at PR agencies Band & Brown and Ruder Finn.