A rugby league player has collapsed and died mere seconds after playing in a regional competition in northern NSW.

Family, teammates and thousands of spectators watched in horror as paramedics tried to revive Narwan Eels prop Alf Atkinson during a NSW Aboriginal Rugby League Knockout semi-final on Monday.

The 34-year-old had played about five minutes of the match at Kingscliff's Ned Byrne Field when he collapsed on the sidelines shortly after being substituted.

He was pronounced dead on arrival at Tweed Heads Hospital from a suspected heart attack.

Teammates at the Armidale club were told the news just prior to their grand final appearance, which they went on to win in his honour 22-18 against La Perouse.

Narwan Football Club chairman Colin Ahoy said the incident had devastated the team.

"We were officially told as a club about 45 minutes after that semi-final that he couldn't be revived and it really affected the players," Mr Ahoy told AAP.

"They played that last game with a lot of emotion."

He said Mr Atkinson's death came as a shock.

"There was no indication whatsoever that there was anything wrong with him," he said.

"(Because) Alf is a pretty big boy, we pulled him off to replace him ... and he had a drink of water and collapsed in front of our bench."

Mr Atkinson was a keen footballer and had played with various clubs, including the Uralla Football Club and the Armidale Rams.

"He loved playing football," Mr Ahoy said.

"Alf was pretty well known by the whole community in Armidale ... he got on with people, he socialised with the community and he was just a good, friendly person."

A collection that was started following the match raised almost $5,000 for Mr Atkinson's family.

AAP