Aitken played three Tests for Scotland during 2016, and while he has represented the Prime Minister's XIII back in 2015, he was never in contention for the Kangaroos squad.
The Warriors' centre and back rower, who will join the Dolphins next year, will provide a steady hand for the Scottish squad alongside another former NRL player in Kane Linnett, who currently plays for Hull KR in the English Super League.
It's the omission of Campbell Graham which will raise the most eyebrows though.
"Representative football is the motivation for a lot of players. Most players have aspirations to play representative football and I'm no different. I want to represent New South Wales and play in the World Cup at the end of the year, whether that's with Scotland or whoever I get selected for," Graham told Yahoo 7 during the pre-season.
Four other Australian-based players - Broncos prop Logan Bayliss-Brown, Parramatta Eels lock Luke Bain, Mackay Cutters hooker Kyle Schneider and young Bulldogs Jersey Flegg player of the year Bailey Hayward have all made the cut.
Scotland Rugby League World Cup squad
Euan Aitken (New Zealand Warriors)
Luke Bain (Parramatta Eels)
Logan Bayliss-Brow (Brisbane Broncos)
James Bell (St Helens Saints)
Ryan Brierley (Salford Red Devils)
Keiran Buchanan (Batley Bulldogs)
Lewis Clarke (Edinburgh Eagles)
Davey Dixon (Dewsbury Rams)
Charlie Emslie (Barrow Raiders)
Dale Ferguson (Dewsbury Rams)
Calum Gahan (London Broncos)
Guy Graham (Whitehaven RLFC)
Bailey Hayward (Canterbury Bulldogs)
Ben Hellewell (Featherstone Rovers)
Liam Hood (Wakefield Trinnity)
Kane Linnett (Hull KR)
Bayley Liu (Sheffield Eagles)
Sam Luckley (Salford Red Devils)
Matty Russell (Toulouse)
Kyle Schneider (Mackay Cutters)
Jack Teanby (York City Knights)
Shane Toal (Barrow Raiders)
Alex Walker (London Broncos)
Lachlan Walmsley (Halifax Panthers)