Eamonn Coghlan was born in Drimnagh and his first running club was the Celtic Athletic Club.
On its break up he moved to the Metropolitan Harriers club where he won the Leinster colleges 5000m title in 1970 and the following year he won the All-Ireland 1500 metres and 5000 metres titles.
In 1971 he was offered a scholarship by Villanova University and joined the famous running coach James 'Jumbo' Elliott. While there the Dubliner won four NCAA individual titles over 1,500metres and the mile. On 10 May 1975 Coghlan ran his first sub 4 minute mile in Pittsburgh, Pennsylvania setting a new Irish record (3:56.2).
One week later, on 17 May, he broke the long standing European Outdoor Mile record of Michel Jazy, in a time of 3:53.3 in Kingston, Jamaica. This record lasted until August 1976.
He graduated from Villanova University with a Bachelor of Science degree in Marketing and Communications.
Coghlan was nicknamed "The Chairman of the Boards" because of his success on indoor tracks winning 52 of his 70 races at 1,500 m and 1 Mile from 1974 to 1987. He set the world record for the indoor mile run with a time of 3.52.6 in San Diego in 1979 and then lowered it to 3:50.6 in 1981
It was improved to 3:49.78 in 1983 at New Jersey's Meadowlands indoor arena and the record stood until 1997 when it was broken by Morocco's Hicham El Guerrouj in a time of 3:48.45. It is still the second fastest indoor mile of all time. It is still a European record.
Coghlan also set the record for the indoor 2000 metres run which stood until Haile Gebrselassie of Ethiopia ran 4:52.86 in 1998.
Coghlan won the Wanamaker Mile at the Millrose Games in NYC's Madison Square Garden a record seven times (1977, 1979–81, 1983, 1985, 1987) his last win being at the age of 34. His record stood for over twenty years with Bernard Lagat winning for an eighth time in 2010:
In 1983 he won the 5000 metres at the 1983 World Championships in Helsinki,
In the 1976 Olympics, he probably made a mistake by taking the lead at 500 metres and John Walker, passed him at 1200 metres with Belgium's Ivo van Damme 2nd and West Germany's Paul-Heinz Wellman in third place. At the 1980 Olympics in Moscow he also finished fourth in the 5,000 metres.
Coghlan won silver at the 1978 European Championships in Prague over 1500 m, behind Steve Ovett of Great Britain, and in 1979, he competed in his only European Indoor Championships (he raced sparingly on the European indoor circuit due to his indoor commitments in the US), taking the gold medal in the 1500m in Vienna.
In 1994, on the Harvard University indoor track, Eamonn became the first man over age 40 to run a sub-four-minute mile. He was 41 at the time.
Since his retirment Coghlan has worked as director of fundraising and development for Our Lady's Hospital and is a regular panellist on RTÉ.
His youngest son, John, is one of Ireland's leading junior athletes and his eldest son, Eamonn, is a golf professional in the United States. His son Michael is an aspiring actor and his eldest, Suzanne, has a career in banking.
In 2008, he served as Grand Marshall for Dublin's St Patrick's Day parade.
Coghlan's book Chairman of the Boards was released in 2008.