Ulster Rugby confirmed Sunday the "tragic death" of Spence, who died along with his father and brother after falling into a slurry tank at a farm in Hillsborough in the Northern Irish region of County Down on Saturday.
Spence's sister, Emma, is recovering in hospital from the effects of fume inhalation. She and Nevin were reportedly attempting to rescue their brother Graham and father Noel, who had already fallen into the tank.
"Nevin was a wonderful player but also a wonderful person," Ulster Rugby chief executive Shane Logan said. "He was well liked by everyone who knew him and his loss will be deeply felt by his teammates and everyone at Ulster Rugby."
A tough-tackling centre, Spence never played a test match for Ireland's senior team but was called up to its training squad during last season's Six Nations competition. He featured for Ireland in a match against the Barbarians in May.
He played three times for Ireland Wolfhounds, the country's reserve side, and was a regular in the Ulster squad, making 42 appearances in total.
Rory McIlroy, the top-ranked golfer from Northern Ireland, and New Zealand flyhalf Dan Carter were among the leading figures in the world of sport to send tributes to Spence.
"Just heard the tragic news of Nevin Spence and his family. Makes you cherish every day you have on this Earth," McIlroy said in a Twitter post.
Spence, who was named Young Player of the Year at the Irish Rugby Union Players' Association awards last year, played for Ulster on Friday in a reserve-team game against Munster in Belfast.
"Nevin was an outstanding young player which was evident from his progression through the representative ranks and the game has been robbed of a very talented young man," Irish Rugby Football Union president Billy Glynn said in a statement.