Welshman Thomas, 37, came close to victory at the Giro d’Italia earlier this year before finishing second to Primoz Roglic.
The 2018 Tour de France winner will compete in the Vuelta for only the second time.
“I’m going there to try and get the best result possible for the team,” Thomas said.
“It will be nice to go for some stages and the GC [general classification] as well, and just see how I’m doing after the first half of the race.”
The Vuelta begins in Barcelona on Saturday, 26 August and ends in Madrid on Sunday, 17 September.
Egan Bernal, the 2019 Tour de France winner, is part of the Grenadiers squad as he recovers from injury.
Jonas Vingegaard, Remco Evenepoel and Roglic will also be part of a strong Vuelta field.
“That’s what motivates you as well, knowing that all the best guys are going to be there, so the goal is to go and do your best and hopefully come out on top,” added Thomas, who made his solitary Vuelta appearance to date in 2015.
“But it’s certainly going to be tough. The bigger the challenge, the more excited you get and the more you want to put into it and try to do well.”
Ineos Grenadiers line-up: T Arensman, E Bernal, J Castroviejo, L De Plus, O Fraile, F Ganna, K Heiduk, G Thomas.
