Seven Dials chief executive Simon Kelner will lead the work, reporting to City AM MD Lawson Muncaster.
Before founding Seven Dials Kelner was the editor-in-chief and managing director of The Independent and worked on the launch of its spin-off daily newspaper i.
Muncaster said: "Seven Dials' entrepreneurial spirit combined with Simon’s experience and understanding of the newspaper industry meant it was a no brainer for us to appoint Seven Dials on an ongoing basis."
Seven Dials’ business director Eleanor Conroy said comms would target both business leaders and younger generations.
"City AM has a much younger audience that the Financial Times, for example, and the readership is growing, so this is both about profile raising and cementing its brand positioning," she added.
Seven Dials’ appointment comes as the paper seeks a replacement for editor Allister Heath, who is joining The Telegraph, and focuses efforts on growing its online readership.
It recently appointed Martin Ashplant to the role of digital and social media director in what the paper stated in a recent editorial was the first of a number of key hires aimed at improving its digital offer.
Under the strategy, it wants to grow from 400,000 unique online users a month to two million by the end of next year.