In his new role, Duffy will report to Ross Belcher, Channel 5’s trading director.
Duffy was promoted to head of broadcast at Aegis in 2011. He was previously at the Aegis-owned Carat.
After starting his career in sales for ITV, Duffy joined Carat as a broadcast manager in 1998. He then moved to Starcom MediaVest Group for one year, after spending six years at Carat, before returning to Aegis.
A Northern & Shell spokeswoman said: "Duffy has a wealth of experience to bring to Channel 5. His knowledge of the agency world will be invaluable as we continue to evolve and strengthen our trading team."