Newcastle says two fans flying to watch the team's football tour of New Zealand were among the 298 people killed on the Malaysia Airlines jet shot down over eastern Ukraine.
The English Premier League club's website named the supporters on Flight 17 from Amsterdam to Kuala Lumpur as John Alder and Liam Sweeney. Ages were not given.
Newcastle manager Alan Pardew says "myself and all the players are deeply shocked and saddened by this terrible news."
The club says Alder was a "familiar sight in the stands for almost half a century, having barely missed a single game in that time." Sweeney had volunteered as a steward on supporters' buses.
They were going to watch Newcastle's preseason tour matches in Dunedin and Wellington, where Pardew and his players will now wear black armbands.