Gameiro, 29, was heavily linked with a move to the LaLiga champions prior to joining Atletico from Sevilla in a deal reportedly worth €32million.
The forward, who has scored twice in six league games for Atletico, said he always knew he wanted to be at the Vicente Calderon.
"There was the possibility of going to Barcelona," Gameiro told Cadena COPE.
"But in my head it was clear I wanted to go to Atletico. When Atleti contacted me, it was clear."
Gameiro said game time would have been difficult at Barca, with Lionel Messi, Luis Suarez and Neymar ahead of him.
