O'Brien will join Nunwood's global insight division in the London office. He joins the agency from TNS where he also worked as an account director. At TNS, he led three large FMCG global accounts and five UK custom accounts.
Separately, Nunwood has appointed Maite Barnett to its Leed's office. Barnett will work as quantitative account director in the global insights division.
Prior to joining, Barnett worked as a research manager for Halifax and Leeds Permanent Building Society.
Additionally, Wunderman's Salina Nawaz has joined Nunwood's London office as senior consultant. Nawaz has more than eight years' experience in the industry and will be joining the market analytics division.
The latest recruitment drive follows last month's appointment of Iain Stanfield, from Leapfrog Research, who joined the global insight division as account director.
Clare Bruce, Nunwood chief executive, said: "Our recent senior appointments are reflective of Nunwood's policy of positioning highly experienced commercial thinkers in key client-facing roles.
"With Nunwood's international business growing apace, we're delighted to have such talented new colleagues onboard."