John Tyrrell comes from a farming background in County Dublin and is a graduate of University College Dublin with an Honours Degree in Agricultural Science, specialising in Animal Production.

Between 1975 and 1978, he worked with ADAS in the UK as a Dairy Husbandry Advisor. In 1978 he joined the Irish Co-operative Organisation Society (ICOS), the umbrella organisation for agricultural co-operatives in Ireland. In 1990, he was appointed Director General of ICOS. He has been deeply involved in the major structural changes which have occurred in the Irish co-operative sector since 1990 including the mergers of co-operatives. This has included chairing of merger negotiations. He has also played an active role in the development of the Irish position on the Common Agricultural Policy, and is on a number of expert groups which the Irish Government has set up to advise an food and agriculture policy.

ICOS advises co-operatives on policy issues, including sectoral policy, co-operative structures and representation of co-operatives' interests at national and international level. It also provides a wide range of services for co-operatives and has long been involved in facilitating the re-organisation of the Irish dairy sector.

He was Vice President of COGECA, the European Association of Agricultural and Fishing Co-operatives from 1996-99. He is also a member of a number of European Advisory Committees including the Common Agricultural Policy Advisory Committee.