Graham has worked for Metro.co.uk for four-and-a-half years, in roles including night site editor and acting news editor.
At Mischief she will chair daily editorial meetings and oversee the replacement of press releases with news copy suited to the different needs of print, online, social and broadcast media. She will also advise on media strategy, media relationships and SEO.
Frankie Cory, CEO of Mischief, said: "Mischief is an agency built on earning attention. News has always been at the heart of that and Daniella's appointment ensures we continue to deliver great stories in the best way."
Graham added: "I believe we can offer something different and exciting for clients, becoming the go-to agency for journalists looking for great stories in the process."