The man, named locally as James Byrne who was in his late 30s and from Lucan, Dublin, was rushed to the Mater Hospital yesterday morning following an accident but was later pronounced dead.
While the exact details of the incident are as yet unknown, it is believed work on moving steel beams may have been taking place at the time.
An investigation by the Health and Safety Authority (HSA) is now under way into the accident, while separate investigations are expected by Dublin Port and Mr Byrne's employers.
A friend and former colleague described him as "an absolutely amazing guy".
"He was just a great guy, really amazing. I am still in shock at the news. He will be a really big loss," the friend added.
Another friend also paid tribute to Mr Byrne.
He said he was "a top quality bloke who always made me feel welcome when I started".
Gardaí and the emergency services were called to Ocean Pier shortly after 11.30am.
An examination of the scene was carried out by officers and inquiries are ongoing.
"Gardaí in Store Street are investigating the sudden death of a man in his 30s following a workplace incident in Dublin Port," a garda spokesman said.
"The Health and Safety Authority and the local coroner have been notified."
Meanwhile, in a separate tragedy in Waterford, a man in his late 50s has died in a farming accident, believed to have taken place on Tuesday afternoon. He was named locally as Maurice Coffey.
Mr Coffey is understood to have died after being crushed against a wall by a tractor, as he was clearing silage on his farm in Kilrossanty.
It is understood he was alone at the time of the accident. His body was found at around 9pm on Tuesday.
The HSA is carrying out an investigation into the accident.
A friend of Mr Coffey told the Irish Independent that "farming was his life" and described him as a quiet man.
His death is the second farming tragedy in the area in just over a year. James Keane died last year in the nearby area of Kilmacthomas when his tractor overturned.