She will be charged with ensuring social strategy is a major focus across the agency.
At Interpublic-owned marketing agency Momentum, Walsh was responsible for the day to day running of EI@UM, the social media joint venture with sister media shop UM London, from April 2010.
She was a communications consultant at Qube Media between 2008 and 2009. Other experience includes freelance stints as a social media strategist and marketing and communications consultant working with local councils.
Walsh was head of communications between 2003 and 2007 at youth advisory firm Connexions Sussex, where she coordinated communication activity across partners and stakeholders, and developed an online community for people working with young people in Sussex.
Ross Jenkins, managing director at Profero Performance, said: "We are delighted Mona chose to join us, having spent a long time trying to find the right person to extend our social offering.
"Mona is immensely talented, with a great understanding of influence and trends within the social media landscape. The fact that Profero is able to attract such talent is a testament to the team we have here, and the work we are producing for some great brands."
Walsh has previously worked with clients as varied as General Mills, Microsoft, Dairy Crest, Marie Curie Cancer Care, American Express and Bacardi.
She said: "Profero has a reputation for delivering great work for wish list brands; and I'll be part of developing and amplifying their already established social offer, which is just the kind of challenge I love.
"I'm really looking forward to getting stuck into the role and working with the amazingly talented team."Follow @MaisieMcCabe