The incident happened on New Street in the early hours of this morning.
A member of the public alerted Gardai that a man had been seriously injured on New Street at twenty past three this morning.
The 28-year-old – who had been stabbed- was taken to Waterford Regional Hospital where he was pronounced dead.
A 35-year-old man was arrested nearby and is currently detained under the provisions of Section 4 of The Criminal Justice Act 1984 at Waterford Garda Station.
The scene has been preserved for a technical examination and the offices of the State Pathologist have been notified.
Gardai are appealing for anyone who may have been in the New Street/John Street area between 3am and 4am today to contact them.