Quin, who will assume a senior post within the agency's five-strong Channel 4 account team, will be responsible for the Film4, More4 and Channel 4 factual brands, which include the documentaries Cutting Edge and Dispatches.
He joins from Naked, where he was the strategy director, and worked across accounts including Dulux, Abbey and Gap. Before that, he was an account planner at McCann Erickson.
Quin replaces Jason Gonsalves, who left Michaelides & Bednash three months ago to join the advertising agency Bartle Bogle Hegarty.
Paul O'Neill, the managing partner at Michaelides & Bednash, said that Quin was an important appointment for the communications agency.
"Channel 4 is a premier account and Andrew will be responsible for driving a significant chunk of it. He is a key hire for us, as he has exactly the kind of skill-set we look for," O'Neill said.
Michaelides & Bednash's clients include GlaxoSmith-Kline, the Design Council, Penguin Books and Diageo. Unilever's Omo and Persil, and Johnson & Johnson's Benecol are other brands on the agency's roster.