The shirt has the colours red, yellow and blue, but some say that from afar the blue appears to have the same purple tone of the Republican flag used from 1931-39.
The flag is still used by those who oppose the Spanish monarchy.
Shirt maker Adidas said there is no political implications in the jersey, and that the design was agreed upon with the Spanish football federation.
Federation officials also said that there is no intended link to the Republican flag. The jersey is a throwback to the one used by Spain at the 1994 World Cup, with a side pattern mixing the three colours.
Spain is in the midst of a political crisis after Catalonia pushed for independence from the rest of the country.