Formerly managing director of Golley Slater Digital, he will be expected to reinforce Flourish's digital skills and grow the company's integrated offering in his new role.
March Smith founded the division and helped it to speedily grow and win clients such as TK Maxx, Euronics and Centreparcs.
It is hoped he will build the digital capability of Flourish and develop online strategies for key clients such as Betfair, Coca-Cola, Camelot, Reed Personnel and newly-won Scope and Samaritans.
Neil Hecquet, co-founder and Director at Flourish, said: "We have hired Matt to show our intentions in the market place and to reiterate to our clients that when they hire us they are hiring the best talent available.
"Our belief has always been that with the right people and the right determination, an agency can win big brands' business without being based in London, and recruiting Matt from a major London agency shows we're prepared to put our money where our mouths are."